History VideoGame / TheBindingOfIsaac

10th Jul '17 2:32:51 AM FlakyPorcupine
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[[caption-width-right:320:Isaac and his mother lived alone in a small house on a hill.]]

to:

[[caption-width-right:320:Isaac and his mother lived alone in a small house on a hill.]]
10th Jul '17 2:32:34 AM FlakyPorcupine
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--> ''"Isaac and his mother lived alone in a small house on a hill..."''

to:

\n--> ''"Isaac [[caption-width-right:320:Isaac and his mother lived alone in a small house on a hill...hill.]]

--> ''"Scrambling around his room to find a hiding place, he noticed a trapdoor to the basement, hidden under his rug. Without hesitation, he flung open the hatch just as his mother burst through his door and threw himself down into the unknown depths below.
"''
1st Jul '17 3:48:27 PM JudgeSpear
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* ArcNumber: 109, the number of coins originally supported by the Greed donation box. The developers teased players about it and misled them into a wild goose chase for secrets, but what it meant is that a certain amount of content was simply blocked off until a patch came out after 109 hours. Coincidentally, 109 also happens to be the in-game ID of the item Money = Power. 109 is also the pickup qu

to:

* ArcNumber: 109, the number of coins originally supported by the Greed donation box. The developers teased players about it and misled them into a wild goose chase for secrets, but what it meant is that a certain amount of content was simply blocked off until a patch came out after 109 hours. Coincidentally, 109 also happens to be the in-game ID of the item Money = Power. 109 is also the pickup ququote for the Dataminer active item in Afterbirth +.
* AsTheGoodBookSays: ''Rebirth'''s theme is titled Genesis 22:10. The verse? "Then he reached out his hand and took the knife to slay his son."
* TheArtifact: The starting room still displays the Move, Attack, Bomb, Item diagrams, but not the keybindings, which can now be changed on the menu.
* AscendedGlitch:
** A certain Womb room would spawn two Larry Jrs and a Chub, but due to engine constraints the Chub would be without her third section and unable to spawn enemies. When the room was ported over to ''Rebirth'', this "buttless Chub" was left in faithfully.
** The Liberty Cap still retains its oddball ability to sometimes act as a compass instead of a mushroom item.
** You can still walk diagonally through spikes and not take damage if you get it pixel perfect. In addition, one possible Curse Room layout has a Red Chest guarded by four "Eternal" fireplaces, and you can walk through those to open the chest if you're careful enough, though you can also blow them up with bombs.
** Conquest could randomly replace War in the Depths 1 in the original game due to a glitch. Here, Conquest is both a Depths 1 and Womb 1 boss.
* AscendedMeme: The in-game description for the Cancer trinket is now "Yay, Cancer!", recognizing a meme that spawned from the people expressing happiness at receiving Cancer (a useful trinket) and [[ARareSentence other improbable phrases]] that only make sense in ''The Binding of Isaac''.
** Additionally, beating [[spoiler: Mega Satan]] as ??? unlocks a multiplayer baby called "[[FanNickname Blue Baby]]".
* BackFromTheDead: ''Rebirth'' continues the trend from ''Wrath of the Lamb'' of making undead versions of existing bosses, in this case applying it for nearly all normal bosses. Note that being undead usually makes each boss even ''more'' dangerous than before.
* BigHeadMode: Entering "[=T0PH EAVY=]" as your seed gives your character [[http://images.akamai.steamusercontent.com/ugc/517134452472044271/DB7F87C0DA17CB7C7AF101057F18130F358939A4/ a head that's at least 5 times bigger than their body.]] On the other hand, entering "[=T1NY D0ME=]" [[http://platinumgod.co.uk/images/seeds/T1NYD0ME.jpg gives you]] [[InvertedTrope Small Head Mode]].
* BigNo: One trinket is a crossed circle whose description reads "NO! Never again!" It removes space bar items from the item pool, which is good when you're collecting stuff to randomize with the D4.
* BlackMarket: In ''Rebirth'', finding a hidden passageway beneath rocks may sometimes lead to a modified shop which lets you pay hearts for shop items instead of coins. It also has a trap door to the next level, all three beggars, and sometimes a slot machine (type varies).
* BlackSpeech: The incomprehensible, guttural chanting in the Sheol theme could count.
* BondageIsBad: A new item in ''Rebirth'', "Gimpy'', is a black leather gimp mask. It's found in the Devil Room for the cost of one heart, or in regular Item Rooms.
* BonusBoss: ''Afterbirth'' plays with this in regards to [[spoiler:Hush]]. You do have to beat it at least once with every character, but unlike [[spoiler:Mega Satan]], this boss does not end the run. Rather, it is an optional diversion that can net you some extra items at the cost of fighting an extra boss, and once you beat it, you go right to [[spoiler:Sheol or the Cathedral]].
* BossOnlyLevel: [[spoiler:The Blue Womb contains two Item Rooms, a Shop, and a single 2x2 room with Hush in it.]]
* BossRush:
** Accessible by beating Mom in under 20 minutes. You have to fight through a total of 30 bosses in 15 pairs, but you're given a free item (out of four choices) to start and a second item if you win (whether they're helpful or not is another matter).
** [[spoiler:Mega Satan summons all the Horseman, all the Super Sins and the Angels during the battle.]]
* {{Bowdlerise}}: Inverted in the credits, which thank everyone who played the [[strike:heck]] hell out of the original.
* BraggingRightsReward:
** Prior to the ''Afterbirth'' expansion, there was no practical reason to beat [[spoiler:Mega Satan]] other than seeing the final ending. There were no unlocks for doing so, no achievements for doing so, not even a mark on that character's boss kill list. [[CosmeticAward All you would receive was a new picture for your save file]].
** With the exception of [[spoiler:the Lost, who has an item unlock for beating every main boss]], Hard mode has no item unlocks, and its associated achievements only require you to beat Mom's Heart/It Lives to unlock co-op babies. Beating the {{Brutal Bonus Level}}s is purely for sport.
** The unlock for beating the BonusBoss with [[spoiler:Keeper]]? Said character starts with a penny. Of course, you're earning that penny by killing what is arguably the hardest boss in the game with a borderline JokeCharacter.
* BulletHell:
** The battles against [[spoiler:Mom's Heart/It Lives, Isaac, ???, and Mega Satan]] offer (a mild example of) this.
** ''Afterbirth'' adds a true example of this, [[spoiler:Hush, an [[BonusBoss extra boss]] that spawns hundreds of enemies and normalizes the damage it takes, meaning even an overpowered build can't just cheese it.]]
** ''Afterbirth +'' has another fine example in the form of [[spoiler:Delirium, the new TrueFinalBoss. He combines complex bullet patterns with impredictable shapeshifting and erratic TeleportSpam. Add his ''massive'' hp and you have a pretty challenging boss in your hands]].
* CallBack: One of the new items in ''Afterbirth'' is actually an old item: [[http://bindingofisaacrebirth.gamepedia.com/Lusty_Blood Lusty Blood]] is just [[http://bindingofisaac.wikia.com/wiki/Bloody_Lust Bloody Lust as it worked in the original Isaac.]]
* CatScare: The final stage of Greed Mode is named [[spoiler: Ultra Greed]]. At the start of the stage, there's a boss room. You enter it, expecting a hard boss battle...[[spoiler: and then a single Monstro (or a pack of Greeds) appears. Ultra Greed is in the ''[[TrickBoss next]]'' [[YourPrincessIsInAnotherCastle boss room]].]]
* CastFromMoney: The Magic Fingers is an item that instantly deals a small amount of damage to every enemy in the room every time you put a penny into it. It has no cooldown time, so if you have lots of money (or are lucky enough to find the Dollar), you can spam it...until your money runs out, anyway.
* ChestMonster: ''Afterbirth+'' added a chest type that looks normal but becomes spiked when you stand right next to it. After some complaints, the chests were redesigned so that the difference between them and standard brown type was more obvious.
* ClassicCheatCode: Some seeds have interesting effects, such as BRWN SNKE ([[ToiletHumor causes Isaac to leave a trail of poop wherever he goes]]) or [=B00BT00B=], described below.
** Taken even further in ''Afterbirth'', where all those special seeds are now available in a list after you put one in, although the icon that indicates the list seems to indicate an EasterEgg, and can be chosen for any play, as well as removing the ability to progress in unlocks with some. They've all but been named cheatcodes. There is even one that makes Isaac invincible: [[spoiler: [=ALM1=] GHTY]]
* CoolHat: The Host Hat, an item introduced in "Afterbirth". It's a [[ExactlyWhatItSaysOnTheTin Host that Isaac wears on his head]]. It protects Isaac from explosions, and has a chance to block incoming shots and counter with the Hosts' signature three-bullet spread.
* ColorCodedForYourConvenience: Champion enemies have traits based on their suit of color, and all of them do one heart of damage rather than half. Dark green means an enemy [[MadeOfExplodium explodes]] at death and drops a bomb, pale red means [[DamageSpongeBoss massive HP]], dark red means regeneration with a double-heart drop, gray deals double damage and drops a key, light blue means it explodes into bullets on death, green leaves a trail of green creep and drops a pill, and dark blue generally means "less dangerous, but can still hurt you" and gives friendly flies.
* ContractualBossImmunity: [[spoiler:[[TrueFinalBoss Delerium]]]] is the only boss with a single phase that is immune to the Chaos Card. It isn't immune to [[TakingYouWithMe Plan C]], which destroys everything in a room and kills you three seconds later, but its death animation takes longer than three seconds. Only Lazarus or a character with Lazarus' Rags (both of which respawn the player in the same room) can make use of this strategy, limiting any unlocks to Lazarus alone.
* CombinatorialExplosion: Part of the update to the game is that this can now happen. The formula is no longer ''"pick up anything that can help you, hope for Mom's Knife or Brimstone"'' for a win that seems assured; now any number of items can assure victory in combination. Two wildly differing examples are Midas Touch + Book of Shadows + Nine-Volt, which basically gives you the ability to go running around turning enemies into coins every 2 rooms, and Ludovico Technique + magnetic tears + shielded tears, which give you a single controllable projectile that pulls in enemies and shots while disabling all shots that touch it meaning that you have control of basically a black hole against your enemies.
** Another mild game-breaker is homing shots plus Technology 1 or 2. The laser beam actually curves itself around to hit enemies.
** A further combo involves Guppy's Hairball and How To Jump. Jump over enemies to avoid them, and the hairball will plow through them. The momentum will also cause the hairball to bounce about well beyond its normal range.
** And pretty much anything plus Brimstone. Homing Brimstone? (if combined with Spoon Bender) Triple Brimstone? (if combined with Third Eye) ''Ten beams firing simultaneously in all directions''...''[[RuleOfThree Brimstone]]''? (if combined with Tammy's Head).
* CoOpMultiplayer: You can sacrifice one of your hearts to allow another player to create and control a familiar. Some of these familiars have special abilities, and some are unlocked by beating [[spoiler: Mom's Heart]] on Hard Mode.
* CounterAttack: Evil (black) hearts inflict the Necronomicon effect on all enemies in the room when a full black heart is depleted. In fact, ''Rebirth'' includes many items that damage enemies when Isaac takes damage. An example is The Negative, the new counterpart of The Polaroid.
* CursedWithAwesome: One of the random curses that you can get inflicted with is "Curse of the Labyrinth", which essentially merges two floors and forces you to fight two bosses in a row at the end. If you get it on the first floor, both treasure rooms will now be unlocked, sparing you the need for one key. On the other hand, later floors can potentially rob you of an additional Devil/Angel Room that could have spawned for both floors.
* DamageSpongeBoss: While there were already bosses who had this as their gimmick, this is taken to extremes as one of many gimmicks for the two new major bosses of ''Afterbirth'', [[spoiler:Hush and Ultra Greed]], who both have health that eclipses the health of every other boss in the game and even normalize the damage you deal to them, meaning that something that would one-shot every other boss in the game will only deal chip damage to them. ''Afterbirth +'' subverts this with [[spoiler:Ultra Greedier]], who has less health than [[spoiler:Ultra Greed]], yet plays this straight with [[spoiler:Delirium]], who doesn't need normalized damage because he has more HP than even [[spoiler:Hush]].
* DamnYouMuscleMemory: An odd variant--the game's new engine will trick some people up. ''Rebirth's'' new engine is extremely powerful, able to handle insane amounts of stuff on the screen at any time at a rock-solid 60fps even on lower-end video cards, but this has some unfortunate effects on people transitioning from the lower, glitchier framerate of the first. People who are accustomed to the half-second pause when transitioning into a room will routinely screw themselves over on hazards, and attacks are much harder to dodge thanks to a lack of HitboxDissonance.
** Most throwable items are used by pressing the appropriate key and aimed using the keys for firing tears. The Chaos Card, however, is automatically thrown in the direction Isaac's body is facing, meaning that it is aimed by walking in the direction you want to throw the card and ''then'' hitting the "use item" key. Woe betide the player who saves one far a particularly tough boss, forgets how to aim it, and ends up throwing it into the bottom wall.
* DarkerAndEdgier: Even though the regular game is fairly grim on its own, ''Rebirth'' has a much more oppressing and bleak atmosphere, compared to the cartoony and lighthearted (if drenched in BlackComedy) atmosphere of the first.
* DarkIsNotEvil: The Dark Bum, a demonic version of Bum Friend with a description of "He wants to take your life"... meaning he wants to take those red hearts that you can't take because your health is full and turn them into soul hearts (and the occasional spider. Being sick sucks). His usefulness (even after two nerfs) and fairly common appearance rate has pretty much made him an EnsembleDarkHorse, complete with [[https://twitter.com/darkbum Twitter page]].
* DeathDealer: Completely literally with the Chaos Card, which instantly kills ''anything'' it hits when thrown. It can even one-shot bosses! [[spoiler:Except [[TrueFinalBoss Delirium]]. [[NoSell It doesn't work on him.]]]]
* DevelopersForesight:
** The various insects you see--not the enemies you're supposed to kill but the actual pixel-tiny insects that add to the atmosphere--are interactive. Shoot or step on one and they'll turn into small puddles of blood. If you shoot a fly, tiny pixels of blood will fly off and they'll actually spiral downwards to the floor! If you have [[BulletDodgesYou the Soul]], bugs will be steered away from you.
** If you're at half a heart left and you enter a new room, [[PottyFailure Isaac will pee a little at the entrance]] showing how terrified he (and possibly you, the player) is at what dangers this new room may present that could end your run.
** In ''Afterbirth'', the Flush item (which normally [[ContractualBossImmunity has no effect on bosses]]) instantly kills [[TalkingPoo Dingle, Dangle, and Brownie]] when used.
** When you defeat Ultra Greed, he turns into a giant gold statue. Midas's Touch will instantly do this, obliterating his armor reduction.
** In ''Afterbirth +'', Glyph of Balance alters the drops of champion enemies so that you'll get what you need the most. If you're almost dead, its first priority is giving you a red heart - unless you have no heart containers, in which case it'll give you a soul heart instead.
* DifficultButAwesome:
** Anti-Gravity Tears can be very difficult to use, but when used well you can simply drag any enemy that chases you through a path of tears, set traps for enemies that love to jump on your head, and burst down enemies that only expose themselves to damage every so often. Goes UpToEleven with Brimstone: It can be difficult to make every laser hit, but you can now fire full-power Brimstone shots ''as fast as you can charge them''.
** Bob's Brain is notorious for blowing up in people's faces and generally being more trouble than it's worth. However, if you can keep track of its respawn time, keep repositioning so it doesn't immediately blow up in front of you, and LeadTheTarget so it hits what you want, it can function as a high-damage grenade launcher that continually replenishes itself. Particularly skilled users can even time it so that it blows up enemies when they're near bomb-able locations, saving on bombs in the long run. It shows up more frequently than a lot of items, giving players more incentive to learn how to use it properly.
* DownerEnding: The endings added by the expansions make it clear [[spoiler:Isaac thought himself to really be corrupt by sin and was driven to suicide]]. The 20th ending in ''Afterbirth+'' puts everything [[MindScrewdriver more or less into perspective]].
** [[spoiler:Isaac starves and suffocates to death inside the chest while hallucinating the entire game. His mother believes him to be missing and only finds out the truth when there are only bones left inside the chest. We then see Isaac walking into the underworld, followed by a demonic shadow.]]
** The Greed mode's ending features Isaac [[spoiler:getting trapped by a cave-in and becoming Greed after hanging himself. In the Greedier ending, his head then comes off and a fountain of bugs gush out of it. [[GainaxEnding How this fits with the other endings is anyone's guess]]]]...
* DunceCap: The Wiz powerup in ''Afterbirth'' is a dunce cap that gives the player character permanently crossed eyes (similarly to the "r u a wizard" pill).
* DyingDream: [[spoiler:''Afterbith+'' reveals that the whole game is this. Even his mother attempting to kill him was allegedly imagined]].
* EarlyGameHell: The hardest parts of Greed Mode are often the early levels, when you have little health and only average tears and damage. Once you've gained a few items, your chances of survival increase dramatically.
* EldritchAbomination: In ''Afterbirth'', collecting three Devil items transforms you into Leviathan (a mini-Cthulhu), which grants flight and a few extra black hearts.
* EnemyScan: The Spider Mod in ''Afterbirth'' gives every enemy (and segments if applicable) a visible health bar so you can track how much damage they've taken. It also displays how much damage your weapons are doing. Finally, the spider familiar itself wanders around randomly and can cause random effects to any enemy that touches it.
* EscortMission:
** Isaac's Heart makes Isaac immune to damage, but generates a heart familiar which takes damage in his place. Enemies will target the heart instead of Isaac, so it has to be protected. On the plus side, Isaac can use any self-damage item for free.
** The Guardian challenge gives you a character with invincibility, flight and a powerful sword to stab monsters with. The catch? You must protect a Punching Bag with Isaac's Heart attached to it. The Punching Bag takes damage, not the heart, and you have no control over how the Punching Bag behaves. You have to escort him all the way to Womb II. Most of the time, [[LuckBasedMission it is impossible]] to prevent the dude from getting hit a handful of times, though at least it tries to avoid traps in rooms. Usually. It's especially bad when you end up with charger-type bosses that can't be knocked off course, which means the Punching Bag is guaranteed to take hits.
* ExactWords: The Suicide King card's description is "A true ending." FromACertainPointOfView, it does just that, since [[spoiler: it drops several items then kills you.]]
* {{Feelies}}: The ''Nintendo Switch'' boxed release includes a fully illustrated instruction manual, which parodies the original ''Legend of Zelda'' game manual, as well as some stickers featuring some of the game's character's and enemies.
* FireWaterJuxtaposition: The new alternate chapters for the Basement and the Caves in ''Afterbirth'', Burning Basement and Flooded Caves.
* GameBreakingBug:
** There seems to be a game crashing bug that crashes the game when enough damage is done to [[spoiler: Mega Satan]] that they die without changing forms. It's rare, but it appears to be very consistent.
** Sad Bombs give bombs a Tammy's Head effect. [[spoiler:Godhead adds a giant halo to each tear.]] There's a glitch that allows one to let loose as many bombs as the screen will handle. Combining all three is the only way outside of [[spoiler:Mega Satan]] to crash the game.
** In ''Afterbirth'', Ending 17 is supposed to be unlocked by defeating [[spoiler:Hush]] at ???, but it only works once. On replays the player receives the exits to the next chapter instead. The problem back when the expansion was released is that imported saves from ''Rebirth'' wouldn't get the ending chest if they already had Chapter 5 unlocked. Trying to enter ??? as some characters would always crash the game, too.
** Alluded to by the ''Afterbirth'' item GB Bug, which has the description "Game breaking bug, right away!" It adds a "glitchy" familiar that bounces around the room inflicting random status effects on enemies.
** [[spoiler:Delirium]] is meant to be completely immune to the Chaos Card but when it gain multiple hitboxes it becomes vulnerable. Which isn't supposed to happen and the game crashes. Time to hope you brought good items.
* GameplayAndStoryIntegration: One of the new rooms is a bedroom where Isaac can sleep in a bed to recover health. In the center of the room, there is a rug. [[spoiler: Blow it up with a bomb to reveal a hatch to the next floor or a crawlspace. You may want to rewatch the intro at this point.]]
* GlassCannon: ''Afterbirth'' added a ''literal'' Glass Cannon, which grants a powerful, reusable shot but also reduces Issac's health to just half a heart. A patch nerfed it hard so it takes away all three kinds of hearts.
* GlassWeapon: In ''Afterbirth'' you can create the Glass Cannon, which is exactly what it sounds like, in [[GlassCannon every sense]]. It's incredibly powerful, but lowers your health to just 1/2 heart, meaning that you'll be killed in a single blow if something hits you.
* GuideDangIt:
** Unlocking [[spoiler:the Lost]] would be a tall order for any one player to accomplish using only the resources made available in game, so much so that the process was ultimately figured out by some people data mining and spoiling it; this unsurprisingly prompted an upset response from creators Edmund [=McMillen=] and Tyrone Rodriguez, who noted it was meant to prompt an [[AlternateRealityGame ARG]]-type response with the community working and speculating to solve it. The process was meant to be a community effort, which probably would have worked eventually, but it is still fairly obscure. You either need to spend a long time going in circles and following vague clues to figure this out, though it should be noted that knowing what to do isn't [[SelfImposedChallenge half]] [[MoonLogicPuzzle of]] [[NintendoHard it.]] [[note]]To put it in perspective, the process involves dying in a certain room holding a certain item in order to receive one part of four images that hint at the actual unlock process, which involves dying with four certain characters in certain locations under certain circumstances in a certain order. ''Consecutively''.[[/note]] The unlock method has been significantly shortened (but made more luck-based) in ''Afterbirth'': [[spoiler: Die with any character in a Sacrifice Room, while holding the Missing Poster. The difficulty is now getting both items to appear in a run, since seeded runs do not work.]] However once you unlock them, you can use them in any run afterwards.
** Two stats are not shown on the stats screen, or elaborated upon at all. You have "Evil / Faith", which is a sliding scale determining what kind of special deal (Deal With The Devil or Deal With The Angel) you get when you qualify for one, and Shot Height, which is used as an alternative to range in some items that claim to increase it (notably increasing Shot Height as Azazel is a ''bad thing'' and makes his range ''shorter'').
** Different damage upgrades are "worth more" than others. Furthermore, some simply add to your damage stat (Damage +1 for instance), while others give you a multiplier instead, or on top of, adding to it, which is significantly better most of the time. The highest of both types are provided by, respectively, Ipecac (+40 damage) and Tough Love (3.2 damage multiplier for each tooth.)
** Special items are back! Not only was this completely unexpected due to Edmund outright saying they would be removed, they now work differently. Instead of the huge list of Special items from the original, there are now only fifteen: [[spoiler:Polyphemus, Mutant Spider, Brimstone, Sacred Heart, Soy Milk (no longer Special in ''Afterbirth''), Pyromaniac, Lil Brimstone, Ludovico Technique, Dr. Fetus, Epic Fetus, the D6, Mom's Knife, Stop Watch, the D100, and Godhead]]. What's more, the Special counter is changed based on sight, not pickup, meaning seeing some of the bad Special items will make it less likely you'll get good ones.
** Lazarus' entire playstyle is bizarre. He starts with a negative Luck stat (-1), and greatly benefits from ''dying'' as early on in the run as possible, since the item he starts with (Lazarus' Rags) give him a damage bonus when he revives.
** Unlocking the Blinding Baby requires you to use The Sun card via the Blank Card activated item. Either you get this one by accident or never figure it out on your own.
* HitboxDissonance:
** The wall-crawling spider type enemies have a damage hitbox that's extremely confusing, placed at least an inch away from the front of the actual model. Since this hasn't been fixed and the crawlers are often protected by a pit, this could be intentional to keep the game from becoming unwinnable by having extremely low range. Still, this can be frustrating when Brimstone and diagonal shots like tiny planet don't hurt them despite visibly touching them.
** This can happen to Isaac himself through size-altering pills. "One Makes You Larger" does ''not'' increase the size of Isaac's hitbox, but it does increase his visual size. "One Makes You Small" ''does'' decrease Isaac's hitbox along with his size.
* InstantRunes: The Black Powder in ''Afterbirth'' causes a trail of black powder to appear where you walk, which dissipates after a certain distance. Forming a circle with the powder forms a glowing red pentagram which damages any enemy that touches it.
* InterestingSituationDuel: The "Challenges" give you certain combinations of items that can drastically alter the way you play. For example, the "When Life Gives You Lemons" challenge mentioned below gives you Lemon Mishap (a JokeItem) and lowers your stats, but also gives you the Nun's Habit, Nine-Volt and a single Lemon Party pill. Since your stats are so bad, you'll have to rely on leading enemies into the damaging puddle dropped by Lemon Mishap until you get better items (but due to the Habit and Nine-Volt, you can use the Lemon Mishap in almost every room, more often if you take damage).
* InterfaceScrew: This game adds three new interfaces curses on top of Curse of the Lost (minimap disabled). Curse of the Unknown removes your health bar, forcing you to keep a mental tally. Curse of Darkness reduces the ambient lightning to almost nothing, though the player and most enemies glow. Curse of the Blind turns every pedestal item (activated and passive items) on the floor into a question mark, including Devil/Angel Room items and shop inventory. It'll make you think twice about picking something up.
* JackOfAllStats: Invoked by the Libra item, which actively balances your stats once you collect it. Can turn the player into a MasterOfNone or MasterOfAll, depending on what items it is mixed with.
* JumpScare: [[spoiler:Ending 3 a.k.a. The Rubber Cement ending.]]
* KaizoTrap:
** Mom's Heart now explodes into a radial bullet burst when killed. It's easy enough to dodge if you know it's coming, but a surprise nonetheless.
** Devil Rooms in ''Afterbirth'' have a chance to contain enemies that you have to kill in order to leave.
* LastLousyPoint:
** ''Rebirth'' is much worse about this than the original, especially with Secret Room items. Since the Secret Room is less likely to spawn items combined with more possible variations, most players resort to exploiting the item pool mechanics to reroll Secret Room items from Beggar drops or mushroom spawns. Another annoying item is Steven, which is now impossible to find except by killing Steven in a main boss fight (already rare to begin with), and only has a 1 in 5 chance of spawning compared to Little Steven. Rerolling also doesn't work on Steven drops, so it has to drop normally.
** Applies much less in Afterbirth: Greed Mode's restocking shops mechanic and expanded shop item pool means it is possible to see the secret room items there. As for Steven, it now drops in Golden Chests.
* LethalJokeWeapon: Because of the improved item synergies, many mediocre items can become the keystone to a weird yet highly effective setup. Bonus points if several if your items are bad but [[AllYourPowersCombined they become effective in tandem with each other.]]
** Lemon Mishap and Pinking Shears, two mediocre-at-best items in ''Wrath of the Lamb'', have been buffed to the point that they can singlehandedly kill bosses.
** "A Card Against Humanity". You'd be surprised at how badly some bosses handle a room full of poop. Becomes even better if you can remotely attack through Ludovico Technique, ???'s Only Friend, or Robo-Baby 2.0.
* LongSongShortScene: The [[spoiler:Blue Womb[=/=]???]] area gets a dang nice song, even though it is simply a single room before a boss fight.
* LuckBasedMission:
** Eden is entirely built around this trope, starting with random stats and items. However, using them requires "tokens", which are acquired by defeating Mom. This is to prevent SaveScumming for a set of good items, though it's easy enough to earn a large surplus if you use other characters consistently.
** "Dice Rooms" are rare rooms with [[ShapedLikeItself a giant die on the floor]]. Stepping on it may re-roll Isaac's items, reroll the pedestal items on the current floor, reroll the pickup items on the current floor, ''restart'' the current floor, or ''several of the above at once''. Using such a room can be the ultimate gamble.
* TheLoad: Familiars have the potential to screw you over to an even greater degree than before, especially when "free-roaming" and "explosives" are dangerously mixed. Special mention goes to the BBF (essentially a friendly Boom Fly) which combines ''both'' and is liable to blow up in your face if the enemy it collides with happens to be near you.
* LuckilyMyShieldWillProtectMe: The Trinity Shield blocks all bullet attacks from Isaac's front, moving with Isaac.
* MagikarpPower:
** One of the new ideas added to the game is the possibility of crippling yourself by picking up a bad item early, Tiny Planet and Bob's Brain to name two, in the hopes that later in the run you'll pick up an item that goes complements them really well, a high attack speed or piercing shots for tiny planet making it better than the pretty inaccurate item it is normally. One could argue it's part of what makes the game more fun than before, just the pure number of items that you might pick up and hold on to in the hopes they work exponentially well with another item you find on the run.
** The Void item added in ''Afterbirth+'' has two properties. This first, which is moderately useful, allows it to destroy any passive items in a room and covert them into random stat boosts, with a chance for a slight range reduction. The second, which applies to this trope, allows it to destroy any spacebar items and permanently copy their effects. There is no limit to how many items can be absorbed this way, and all of them will trigger each time Void is used. This can include generating Soul Hearts, Black Hearts, Eternal Hearts, mapping a floor, using Blank Card and its combos, Placebo and its combos (most importantly, '''infinite charge'''), four-way Brimstone from Krampus, and so forth. The only things it can't copy are spacebar items that are consumed upon use.
** Also in ''Afterbirth+'', the Smelter item. It takes 6 rooms to charge, and each use removes Trinket(s) and permanently applies its effect to Isaac. If you happen to find Mom's Box or a Fortune Teller machine, you'll quickly become unstoppable.
* MarathonLevel: The new VeryDefinitelyFinalDungeon, [[spoiler:the Void]], is this. It's as large as two XL Womb floors put together and has 6 or 7 boss rooms besides the FinalBoss fight, one of which always contains another "final" boss. Good luck finding your way there if you get hit by Curse of the Lost.
* MurderSuicide: [[InvokedTrope Invoked]] by a new item in ''Afterbirth +'', the Plan C. It instantly kills ''anything'' in the room (even final bosses)... and kills you shortly afterwards.
* MusicIsEighthNotes: The Dingle boss whistles to summon mooks. The audio is accompanied visually by a few eighth notes.
[[/folder]]

[[folder:N-Z]]
* {{Nerf}}: An inevitable result of re-balancing the game from ''Wrath of the Lamb'', several items and one character (Cain) were weakened for balancing purposes. On the flipside, Samson received a much-needed buff.
** The Bloody Lust mechanic change to powering from Samson taking hits instead of getting kills is a significant change of strategy for the worse due to his starting health.
** An ''Afterbirth'' patch nerfed Lilith's Box of Friends and Azazel's Mini Brimstone laser's power and charge time. Another patch un-nerfed Azazel's damage, but made his charge time ''worse''.
** ''Afterbirth'' also nerfed Judas's Book of Belial to only increase the chance of getting a Devil/Angel Room when held instead of guaranteeing one whenever possible.
** A patch for ''Afterbirth'' made a very controversial nerf to the [[PurposefullyOverpowered Stopwatch]]. Instead of having it slow down every enemy permanently, it was changed to activate only after taking damage ''and'' having its effect only last for one room. Many people were visibly upset by this, and in a later patch, while it kept its flaws, it was changed to [[ObviousRulePatch also activate if Holy Mantle's shield was broken]], which at least still makes it a very useful item when playing as [[spoiler:The Lost]].
* NewGamePlus: In ''Afterbirth +'', if you defeat the Lamb as your FinalBoss, you're given the option to do a "Victory Lap". You start from the first level with all your items intact. This can be done endlessly, and the game tracks how many times you repeat. Most achievements won't work in this mode (only the "U Broke It!" achievement can be earned on a Victory Lap). Further, on the third victory lap, the game increases in difficulty (you are turned into [[spoiler:the Lost]], minus his Holy Mantle and D4, and shops no longer appear).
* NiceHat: ''Afterbirth'' introduces the item Host Hat, which puts a Host on Isaac's head. The item's in-game description is even "Nice hat!"
* NintendoHard: A "hard" difficulty level has been added, which significantly dials up the amount of enemies and [[EliteMook champions]] while giving you less powerful items. ''Afterbirth+'' does this for Greed Mode, which is called Greedier Mode.
* NoFairCheating: Level seeds allow you to repeat a powerful run, but block any achievements. Similarly, challenge maps only allow you to unlock the associated achievement. Finally, the NewGamePlus blocks any achievements.
* NotTheIntendedUse:
** The [[spoiler:key pieces from the Angels]] are supposed to be used to unlock the TrueFinalBoss. However, if the player's objective is the regular boss of that floor, then these items can be rerolled with the D6, allowing for an extra Angel Room item. Players can also bet on getting Dad's Key later to sidestep the problem, but this is less likely.
** Also, Dead Cat (which gives you nine lives...at the cost of only having a single heart container for each life) can be used to purchase every Devil Room item for basically free: you pay for the Devil Room item with your last heart, you die, you get resurrected, you go back into the Devil Room, pick up the other Devil Room item, die again, get resurrected again, continue to the next floor with 7 lives remaining and two free items! If you're good at dodging, you probably don't need all nine lives anyway.
* OneHitKill: The Chaos Card kills almost anything in one hit. The only things that can survive it are [[spoiler:the first form of Satan, the first form of Mega Satan, Delirium ([[ContractualBossImmunity which is the only intentional exception]])]], and, likely due to a bug, Scolex.
** Plan C takes it a step further by [[SmartBomb instantly killing everything in the room]]. [[spoiler:Including Isaac.]]
* PajamaCladHero: The PJs ''"make you feel cozy"'', which shows by healing Isaac to full health and giving him four extra soul hearts on top of that.
* PowerUpLetdown:
** The general opinion of Bob's Brain. It's a minion/follower that charges into enemies in a straight line when "fired" along with Isaac's tears, exploding on contact. It will do this even if the enemy is right next to Isaac, causing him to take SplashDamage. It also doesn't explode on the return trip if it misses, making it hard to aim, and doesn't synchronize well with tears. BBF (Big Beautiful Fly) also falls into this category for exploding upon contact with enemies (regardless of location) though at least BBF's movement is predictable and can be accounted for.
** Thought that Samson or [[spoiler:???]] wasn't worth the effort in the original? The crappy reward-to-effort ratio for [[spoiler: The Lost]], a genuine JokeCharacter, is even ''worse''.
** The Suicide King special tarot card requires beating one of the more infuriating challenges to unlock and has the splendid effect of dropping 10 items... and killing you.
** The Lord of the Flies transformation gives you flight, and makes all enemy flies into friendly blue flies. That's about it... At least it's free flight, but Guppy is far superior.
** The new transformations in ''Afterbirth'' range from helpful to nearly pointless. The Mushroom, for example, is just a free Health Up.
** Tiny Planet, which makes your shots orbit you at a fixed distance instead of going forward... which makes it almost impossible to hit anything with more than half your shots, forces you to fight at close range, and makes knockback useless for defense. At least it works differently with a few alternate attacks (notably Brimstone).
** Curse of the Tower, unless you have an item that provides bomb immunity or invincibility after being hit. It spawns a handful of troll bombs any time you take damage, dealing lots of damage to anything in the room--but possibly also damaging you again. And it will destroy any blood donation machines or demon beggars you try to use.
** If you manage to defeat one of the hardest bosses in the game with the Keeper, one of the hardest characters in the game, you are rewarded with... him starting with a single penny in future runs. Gee, thanks.
** The Wiz allows Isaac to shoot tears out of both eyes at once, but also forces him to shoot diagonally (effectively a permanent "R U A Wizard" effect). Given that the game is designed around shooting in the cardinal directions, it's generally more of a hassle than a benefit.
* PromotedToPlayable: Some of the hidden items from the original game are now unlocked from the start in ''Rebirth''. Other items now have different unlock requirements, such as The Nail. And inverted with a few items that didn't need to be unlocked in vanilla, such as the Wire Coat Hanger.
* PurposelyOverpowered:
** The Stopwatch. Unlocking it requires you to put 999 coins in the Donation Machine (which can take dozens of runs since the Donation Machine will randomly jam and refuse further donations for that run). Once you have it, it slows down all enemies and their bullets for the duration of that run, making it a near-cakewalk. It got hit with a huge nerf in ''Afterbirth'' via a patch, reducing it to an on-hit, single room effect (still pretty good against bosses, but not quite as useful overall).
** The Mega Blast is Brimstone or Krampus' Head on crack. It gives you Mega Satan's giant Brimstone laser, which lasts a solid 15 seconds and persists between rooms, allowing you to steamroll through numerous rooms before the laser runs out. However, this requires beating [[spoiler:[[HarderThanHard Mega Satan]]]] with every character, including the JokeCharacter AND it's the only item in the game with a 12-room charge (and batteries only refill 25% of the charge bar), so you'll only be able to use it once every two floors, or once a floor if you're lucky. With the addition of Void in ''Afterbirth +'', you can even bypass the long charge time.
** Mama Mega! is this. When used, it deals kills every normal enemy in a room (if an enemy spawns another upon death, you have to kill them yourself), does massive damage to bosses, destroys all forms of rocks (but not Keepers or rocky chests), opens all Secret and Super Secret Rooms, and even opens the paths to Boss Rush and the Blue Womb if you've passed the time limit for either. Best of all, it lasts for the entire floor on which it is used. It basically gives you an entire "free" floor with nothing standing in your way.
* RecurringBoss:
** Depending on your choices and luck, you may fight The Fallen as a boss four times in a single run: once at a random level, once during the boss rush, once as a Double boss in the Womb, and once guarding Satan. Not counting the times it shows up as a regular room enemy and its slight recoloring Krampus.
** Similarly, the Greed/Super Greed battle is almost guaranteed to replace one of the shop rooms or secret rooms you've striven to unlock. Bonus points if the two show up on consecutive floors. He's so common, that a trinket, [[spoiler:Greed's Rib]], added in ''Afterbirth'', prevents any form of Greed from appearing.
** There are four completely different Gurdy bosses for various stages in her life cycle, which can be fought in each of the four main areas of the game. You can potentially fight them all in one run.
** In Greed mode, you are naturally quite likely to fight several copies of Greed and/or Super Greed on the penultimate level, then fight several more copies at the beginning of the final level. And then you fight Ultra Greed.
* {{Retraux}}: ''Rebirth'''s art style is intended to resemble a colorized Gameboy game. Additionally, there is an arcade filter available by using the [=B00BT00B=] seed code. ''Afterbirth'' adds a Retro Vision pill which pixelates the screen on and off for a minute or so.
* RockMeAsmodeus: ''Hericide'', [[spoiler:Satan]]'s new boss theme.
* SaveScumming: Intentionally discouraged with the increased item synergies in the hopes that players stop immediately restarting when they get a bad item early on. Then again, the seeding tools provide for a form of this if one gets particularly lucky with their game's generation and want to retry after dying partway through.
** Also discouraged with Eden. Eden starts with random stats and items, so selecting Eden requires and consumes an Eden Token gained by beating end-game bosses. But if you're a good enough Isaac player you'll have more Eden Tokens than you know what to do with.
** By forcing the game to quit before the Game Over screen comes up you can reload your last suspend save, but never collect Guppy's Collar while doing this. The game forces 1-up effects when you save scum and the Collar works by either reviving or killing you.
** ''Afterbirth +'' punishes repeated resets with the Mr. Resetti achievement: it unlocks [[PowerUpLetDown half soul hearts]] for the next runs.
* SchmuckBait: There's an unlockable tarot card called [[spoiler:Suicide King.]] Upside, it spawns a bunch of cool pickups. Downside? [[spoiler:[[ExactlyWhatItSaysOnTheTin You die]]]].
* SecretCharacter: A new one for this version. [[spoiler:"The Lost", a OneHitPointWonder incapable of gaining [[OneHitPointWonder any hearts]] and starts with flight.]] Unlocking him is a real GuideDangIt: the old way was to [[spoiler:die to Mullibooms as Isaac on the basement, then to your own bombs as Maggie in the caves, then to Mom as Judas, then to Satan stage 2 as Azazel, with no deaths in-between and in that order.]] In ''Afterbirth'', you just have to [[spoiler:kill yourself in the Sacrifice Room with the Missing Poster in your inventory]].
** Another one was added in ''Afterbirth'': [[spoiler:The Keeper. He uses coins for health and converts all hearts into blue flies. He can only have up to 2 coins worth of health at a time, yet while he can't gain any, he can still ''lose'' them. On top of that, he's slow and fires triple shots at reduced speed.]]
* SequelDifficultySpike:
** Zig-Zagged. ''Rebirth'' adds a lot of new content while updating older items from the original, which makes things both more difficult and easier thanks to the new items but larger item pool. The shop gets a major revamp with a lot of very useful items to potentially buy. The main bosses are a straight example, all of them having been given new moves and BulletHell abilities which make the fights twice as hard as they were in the original game.
** The ''Afterbirth'' expansion adds new features to the level design such as cramped rooms and trap rooms. Multiple bosses at cramped rooms don't mix well. And certain trap rooms only give you a split second to react before a bomb explodes in your face. There are also trapped treasure rooms which might require you to use a bomb to reach the item.
* SillinessSwitch: Some special seeds you can type in have strange and sometimes hilarious effects. For example, FART SNDS turns all sound effects in the game into, you guessed it, fart sounds. Find a nickel? ''Pffrt''. Open a door? ''Ffrrp''. Take damage? ''Prpfff''. Another good one is SLOW 4ME2, which increases or decreases the background music tempo depending on how fast you're moving.
** As of ''Afterbirth'', inputting a special seed permanently unlocks its effect, and ''any number'' can be toggled in a new [[EasterEgg menu of Easter Eggs.]][[labelnote:Spoiler]]Press Q (or LB) on the character select screen.[[/labelnote]]
* SolidGoldPoop: In ''Rebirth'', any run-of-the-mill poop piles you find have a chance to be golden poop piles, which drop a bunch of coins or the Counterfit Coin trinket when destroyed. [[spoiler:Having The Poop active item and Midas' Touch will let you spawn these every single room.]]
* SpeedRun:
** Now actively encouraged, since many features were added to help out the dedicated SpeedRun community. All runs have an internal timer attached to them (viewable by pulling up the map, which also displays the current level for screenshot purposes) and the game keeps track of your best times for fresh runs as each character (i.e. randomly generated, not from a seed). The main purpose of seeds was to allow for many people to play the same run and compare completion times, since without seeds the times were too often influenced by the RandomNumberGod. There are now leaderboards for the quickest runs for a particular daily seed and [[SeriousBusiness competitive speed-running]] may very well arise.
** Additionally, beating Mom in under 20 minutes grants access to the special BossRush room. The little clock that's visible during each loading screen shows how much time is left until this room expires, and you can bring up the map to check your current time.
** The Speed! challenge requires you to beat It Lives in 16 minutes, or every 10 seconds you take a half-heart of damage. On top of that, all enemies and their bullets move twice as fast.
** In ''Afterbirth'', defeating Mom's Heart/It Lives in under 30 minutes grants access to [[spoiler:The Blue Womb and the BonusBoss Hush]].
** In ''Afterbirth+'', one achievement (and a new item) can only be unlocked by beating the Lamb in under 20 minutes. [[ThatOneAchievement Good luck with that.]]
* SpreadShot: Where to start? Several enemies use these, and there are ''many'' items that allow the player to fire in spreads.
* StandardStatusEffects: The Iron Bar item adds a Concussion tear effect, which confuses enemies. The Charm tear effect causes enemies to actively seek out and damage other enemies, if they are capable of doing so (enemies stuck on a certain path, such as rolling guts, don't seek out other enemies); the charmed enemy can still damage you, however. The Fear tear effect causes enemies to slowly run away from you, and stops some enemies from firing at you. The Fire tear effect deals some brief continuous damage after hitting an enemy, and causes occasional fiery explosions. The Slow and Poison effects return from the original game. They're unchanged except affected enemies now have an icon above their heads.
* StealthPun: The Latchkey gives you [[LockAndKeyPuzzle Luck and Keys]].
* {{Stonewall}}: One of the new items, Punching Bag, gives you a friendly Mulligan that acts as a tank for you.
* StuckItems: You're still stuck with whatever is held in your use slot like in the first game until you find another usable item. However, it's thankfully averted with pills, trinkets and tarot cards, which can be dropped by holding down the map button (or the left Ctrl button on your keyboard). But even the map button cannot get rid of the Tick trinket, which is the one truly irremovable item in the game.
* SuperPrototype: Technology 0.5 is a far superior laser when compared to Technology and Technology 2. It doesn't replace your regular tears so is a direct firepower upgrade when you pick it up, doesn't have a damage multiplier reduction built into its stats and perfectly synergizes with your power-ups. It also randomly adds power-up effects. Its only downside is that it occasionally misfires, but you'll barely even notice it.
* SuspiciousVideoGameGenerosity: The item pool got buffed ''again'' from ''Wrath of the Lamb'' by introducing items that confer benefits worth two separate items from "Vanilla" ''Isaac''. You'll need those buffs for sure...
* TalkingPoo: The Dingle boss, and his minions (Squirts).
** ''Afterbirth'' adds [[PaletteSwap Dangle]] and Brownie.
* ThemeNaming: The {{Disc One Final Boss}}es [[spoiler:and ''Rebirth''[='=]s True Final Boss]] all have boss themes that end in ''cide''. (''Matricide'', [[spoiler:''Ventricide'', ''Hericide'', and ''Infanticide''.]] Averted with the [[spoiler:fake]] {{True Final Boss}}es, who have uniquely named themes ([[spoiler:''Ascension'' and ''The Fallen Angel'']])
* ThiefBag: In ''Afterbirth'', money bags will occasionally spawn that drop a few bombs, coins, or keys when grabbed.
* TooAwesomeToUse:
** The Friendly Ball allows you to "capture" an enemy and release it to fight with you until it dies, persisting between rooms and floors. However, since the item has a 4-room recharge, it can take at least eight rooms in order to successfully release an enemy you captured, and even then your new companion will most likely die after a couple rooms.
** Mega Blast is an activated item which fires a massive Brimstone laser which does insane damage and persists between rooms and floors, lasting for fifteen seconds. However, not only does it have a 12-room recharge (the only item in the game to require that many rooms), but the battery pickup will not fully recharge the item for another go. Because of this, Mega Blast tends to be saved for endgame floors/bosses that players want to wipe out quickly, such as the [[DamageSpongeBoss insanely tanky]] BonusBoss.
** The Chaos Card can OneHitKill ''literally anything'' in the game. The catch, of course, is that it's a card and can therefore only be used once. Like Mega Blast above, the Chaos Card tends to be saved for endgame bosses such as said insanely tanky BonusBoss. Unless, of course, the player gets a Blank Card...
** Diplopia is an activated item that doubles every pickup and collectible item in the room. With the number of items in the game that stack with themselves, this can create some insane synergies. However, it's only good once, and you can't cheat by using the ? Card to duplicate its effect because doing so consumes Diplopia anyway for no additional benefit. It often comes down to a decision regarding whether to use it on the decent item you have in front of you, or to hold onto it in hopes of getting a better item to duplicate later on.
* TookALevelInBadass: A number of characters, playable and otherwise:
** Mom's Heart/It Lives was a rather straightforward FlunkyBoss in the original game. This time around... let's just say that BulletHell veterans will feel right at home.
** [[spoiler:Isaac/???]] likewise get a bullet hell buff and new attacks.
*** Isaac's third form is [[InvertedTrope considerably easier]] in Rebirth - his light attacks are easy enough to avoid as you can guess the pattern of the safe zones, plus his bullet hell attack has a much shorter range, is easier to dodge and is not homing. And he doesn't spawn angels in this phase.
** Eve has more health and Whore of Babylon kicks in at one full heart instead of a half, allowing her to take advantage of the serious damage buff while still being able to endure a blow from most early game enemies, giving her a chance to build up a buffer of spirit hearts.
** Samson has much more health, increases damage done for every hit he takes, has much larger range, and keeps accrued bonuses across the entire ''floor'' instead of just the room.
** Most characters receive an upgrade to their starting load out once certain conditions are met. Such as Cain starting with the Paper Clip (unlocks Gold Chest for free) or Eve starting with the Razor Blade (boost damage for the room at the cost of a heart, letter her trigger Whore of Babylon at will).
* TrueFinalBoss: Attempts always end after a certain boss, though unlocking more stuff and meeting certain requirements can result in the bar being raised on who is considered the final boss; for example, the very first run ends with Mom at stage six, though beating her a second time spawns the door to the next stage, where players have to fight the new final boss, [[spoiler:Mom's Heart]]. Assuming everything is done perfectly, you have to reach the credits ''eighteen'' times to unlock TheVeryDefinitelyFinalDungeon and face the [[spoiler:8]]th final boss.[[labelnote:exp.(spoilers!)]]First run ends at Mom, unlocks Womb; eleven runs to unlock It Lives! and Cathedral/Sheol access; five runs to kill Isaac/Satan to unlock The Chest/The Darkroom access; one run to kill either ???/The Lamb and spawn the Golden Gate.[[/labelnote]]
** However, with a bit of SequenceBreaking using [[spoiler:a Devil Room that spawns after the Mom's Heart fight, which always leads to Sheol even if you haven't yet unlocked It Lives!]], one can theoretically reduce this to eight runs[[labelnote:exp.(spoilers!)]]1 run to unlock the Womb, 1 run with the Devil Room to defeat Satan (and unlock Judas, whose starting item guarantees a Devil Room will spawn whenever possible), 5 more runs to unlock the Negative, 1 run to defeat the Lamb and unlock the Golden Door.[[/labelnote]]. Still quite a few runs though.
** In ''Afterbirth '' there is the True ''True'' Final Boss in the [[TheVeryDefinitelyFinalDungeon Truly Final Dungeon]], [[spoiler: Delirium]].
* UnexpectedGameplayChange: Some challenges take away your tears completely and force you to fight with either attack familiars or a recharging spacebar item and maxed bombs.
* UniqueEnemy:
** There's a blue-skinned variation of the Conjoined Fatty monster that has a very slight chance of appearing in the I AM ERROR room and [[spoiler:the Chest]]. Despite what its appearance may imply, it's completely distinct from a champion variant and attacks with vicious homing Ipecac shots.
** The bosses [[spoiler:Hush]] and [[spoiler:Ultra Greed]] spawn Gapers that are reskinned to fit the respective boss's motif. [[spoiler:Hush]] also spawns uniquely-skinned Ring Flies that form more complex formations than the normal variety and reskinned Boils with a different attack pattern.
** Two Stone Grimace varieties are extremely rare and only appear in one floor. One is the Broken Gaping Maw, which alternates between trying to suck the player character in with more force than the normal Gaping Maws and not doing anything, found only in [[spoiler:the Womb]] and neither of its alternate floors. The other is the Brimstone Grimace, which fires brimstone lasers and can only be found in [[spoiler:Sheol]]. It is possible to play the game for a long time through several runs without even seeing either of them.
* UnwinnableByMistake: The Blue Bomber challenge turns off your tears but gives you the Kamikaze spacebar item and Pyromaniac (immunity to bombs). Some enemies, however, are immune to Kamikaze, so you need bombs or another source of damage to kill them. If you have neither, you have to reset. Mercifully, a patch added [[CherryTapping Brother Bobby]] to the player's arsenal, which prevents the situation from being ''completely'' unwinnable.
* UpToEleven: ''Afterbirth'' has the XXXXXXXXL challenge, which is the "XL" level effect on steroids. All levels have a size which is roughly equal to an XL Womb level.
* VariableMix: If the room has a lot of enemies or there's a miniboss, an electric guitar harmony fades into the music.
* ViolationOfCommonSense: With a hard cap of 12 hearts compared to the original having no cap at all, it's actually to your benefit to only have a few red hearts. Having full health means you will be unable to pick up spirit hearts or the new black hearts (which deal full room damage when depleted, similar to the Death tarot card). This means runs in which a low number of health containers are found may actually be more viable. It also seems that spirit hearts are a bit more common, and black hearts are more likely to pop up than you might expect for something so useful.
* WesternZodiac: The 12 signs of the zodiac appear as upgrades for Isaac.
** Aries increases speed and lets you deal damage to enemies by running at them.
** Taurus slows the player down, but when in a room full of enemies you build up speed over time, eventually getting the My Little Unicorn effect.
** Gemini gives Isaac a little buddy attached to him that attacks enemies when they get close.
** Cancer gives 3 soul hearts and makes all damage reduced to 1/2 a heart when he takes damage in a room.
** Leo allows the player to break rocks, mushrooms, skulls, etc. by stepping on them.
** Virgo has a chance to make the player invincible after taking damage and makes all negative pills positive.
** Libra balances the player's stats and gives 6 coins, bombs, and keys.
** Scorpio gives the player's tears poison effects.
** Sagittarius makes the player's tears penetrate enemies and increases speed.
** Capricorn increases all stats.
** Aquarius leaves a trail of tears behind the player, damaging enemies that step in it.
** Pisces increases tear fire rate and the amount of knockback enemies take from tears.
** Finally, the Zodiac item takes the effect of a random zodiac sign every floor.
* WhamEpisode:
** The 15th and 16th ending. [[spoiler: Respectively, Isaac is shown to have gone missing, with his mom searching for him, and Isaac turns into a demon!]]
** Ending 17 and 18. [[spoiler:The first confirms Isaac died trapped inside the chest. The latter is another take on his death: he's crushed by debris while trapped on some cave and his corpse becomes Greed.]]
** Ending 20. [[spoiler:His mother trying to kill him was imagined. Isaac killed himself by locking himself up in the chest because he blamed himself for his family falling apart, thinking that he was corrupted by sin]].
* WingedSoulFliesOffAtDeath: The new death animation. [[spoiler: And it's a top secret character, called "The Lost"!]]
* AWinnerIsYou: Inserting coins into the Greed Donation Machine grants you a few unlocks for the first hundred or so. Originally, it stopped at around 109, but a patch allowed the player to set the donations towards 999, which does nothing but praise the player with fireworks at the end and award an achievement. [[spoiler:But something major happens if you donate one more coin...]]
* WhenLifeGivesYouLemons: The name of Challenge #12.
* WorldOfSymbolism: ''Isaac'' explores the same themes as most of Edmund [=McMillen=]'s older games, such as ''VideoGame/TimeFcuk'', but uses very different imagery to do so.
* WrapAround: The Continuum item grants this effect to your tears, causing them to pass through walls and emerge from the opposite side.
[[/folder]]
----
-> [[TheStinger Dear Diary]],
-> [[TvTropesWillRuinYourLife Today I died]]. I was killed by this page on [[Wiki/TVTropes some wiki]]. (ugly)
-> I leave all that I own to my pet cat Guppy. (Pretty cool stuff!)
-> Goodbye cruel world,
-> -XOXO Troper
----
1st Jul '17 3:51:04 AM GojiBiscuits
Is there an issue? Send a Message


** Brimstone. It has fantastic range, but only becomes the BreathWeapon it really deserves to be if your damage is high enough, and surprisingly requires some strategy to use correctly, as you have to charge the beam before firing it. If you combine it with Spoon Bender (for homing abilities), it becomes significantly more effective and can lock onto multiple enemies at a time in one shot, and if you pick up Tammy's head... you become effectively invincible, and a master of BeamSpam! You'd better hope that you can find all three items in the same run, though...



* ArcNumber: 109, the number of coins originally supported by the Greed donation box. The developers teased players about it and misled them into a wild goose chase for secrets, but what it meant is that a certain amount of content was simply blocked off until a patch came out after 109 hours. Coincidentally, 109 also happens to be the in-game ID of the item Money = Power. 109 is also the pickup quote for the Dataminer active item in Afterbirth +.
* AsTheGoodBookSays: ''Rebirth'''s theme is titled Genesis 22:10. The verse? "Then he reached out his hand and took the knife to slay his son."
* TheArtifact: The starting room still displays the Move, Attack, Bomb, Item diagrams, but not the keybindings, which can now be changed on the menu.
* AscendedGlitch:
** A certain Womb room would spawn two Larry Jrs and a Chub, but due to engine constraints the Chub would be without her third section and unable to spawn enemies. When the room was ported over to ''Rebirth'', this "buttless Chub" was left in faithfully.
** The Liberty Cap still retains its oddball ability to sometimes act as a compass instead of a mushroom item.
** You can still walk diagonally through spikes and not take damage if you get it pixel perfect. In addition, one possible Curse Room layout has a Red Chest guarded by four "Eternal" fireplaces, and you can walk through those to open the chest if you're careful enough, though you can also blow them up with bombs.
** Conquest could randomly replace War in the Depths 1 in the original game due to a glitch. Here, Conquest is both a Depths 1 and Womb 1 boss.
* AscendedMeme: The in-game description for the Cancer trinket is now "Yay, Cancer!", recognizing a meme that spawned from the people expressing happiness at receiving Cancer (a useful trinket) and [[ARareSentence other improbable phrases]] that only make sense in ''The Binding of Isaac''.
** Additionally, beating [[spoiler: Mega Satan]] as ??? unlocks a multiplayer baby called "[[FanNickname Blue Baby]]".
* BackFromTheDead: ''Rebirth'' continues the trend from ''Wrath of the Lamb'' of making undead versions of existing bosses, in this case applying it for nearly all normal bosses. Note that being undead usually makes each boss even ''more'' dangerous than before.
* BigHeadMode: Entering "[=T0PH EAVY=]" as your seed gives your character [[http://images.akamai.steamusercontent.com/ugc/517134452472044271/DB7F87C0DA17CB7C7AF101057F18130F358939A4/ a head that's at least 5 times bigger than their body.]] On the other hand, entering "[=T1NY D0ME=]" [[http://platinumgod.co.uk/images/seeds/T1NYD0ME.jpg gives you]] [[InvertedTrope Small Head Mode]].
* BigNo: One trinket is a crossed circle whose description reads "NO! Never again!" It removes space bar items from the item pool, which is good when you're collecting stuff to randomize with the D4.
* BlackMarket: In ''Rebirth'', finding a hidden passageway beneath rocks may sometimes lead to a modified shop which lets you pay hearts for shop items instead of coins. It also has a trap door to the next level, all three beggars, and sometimes a slot machine (type varies).
* BlackSpeech: The incomprehensible, guttural chanting in the Sheol theme could count.
* BondageIsBad: A new item in ''Rebirth'', "Gimpy'', is a black leather gimp mask. It's found in the Devil Room for the cost of one heart, or in regular Item Rooms.
* BonusBoss: ''Afterbirth'' plays with this in regards to [[spoiler:Hush]]. You do have to beat it at least once with every character, but unlike [[spoiler:Mega Satan]], this boss does not end the run. Rather, it is an optional diversion that can net you some extra items at the cost of fighting an extra boss, and once you beat it, you go right to [[spoiler:Sheol or the Cathedral]].
* BossOnlyLevel: [[spoiler:The Blue Womb contains two Item Rooms, a Shop, and a single 2x2 room with Hush in it.]]
* BossRush:
** Accessible by beating Mom in under 20 minutes. You have to fight through a total of 30 bosses in 15 pairs, but you're given a free item (out of four choices) to start and a second item if you win (whether they're helpful or not is another matter).
** [[spoiler:Mega Satan summons all the Horseman, all the Super Sins and the Angels during the battle.]]
* {{Bowdlerise}}: Inverted in the credits, which thank everyone who played the [[strike:heck]] hell out of the original.
* BraggingRightsReward:
** Prior to the ''Afterbirth'' expansion, there was no practical reason to beat [[spoiler:Mega Satan]] other than seeing the final ending. There were no unlocks for doing so, no achievements for doing so, not even a mark on that character's boss kill list. [[CosmeticAward All you would receive was a new picture for your save file]].
** With the exception of [[spoiler:the Lost, who has an item unlock for beating every main boss]], Hard mode has no item unlocks, and its associated achievements only require you to beat Mom's Heart/It Lives to unlock co-op babies. Beating the {{Brutal Bonus Level}}s is purely for sport.
** The unlock for beating the BonusBoss with [[spoiler:Keeper]]? Said character starts with a penny. Of course, you're earning that penny by killing what is arguably the hardest boss in the game with a borderline JokeCharacter.
* BulletHell:
** The battles against [[spoiler:Mom's Heart/It Lives, Isaac, ???, and Mega Satan]] offer (a mild example of) this.
** ''Afterbirth'' adds a true example of this, [[spoiler:Hush, an [[BonusBoss extra boss]] that spawns hundreds of enemies and normalizes the damage it takes, meaning even an overpowered build can't just cheese it.]]
** ''Afterbirth +'' has another fine example in the form of [[spoiler:Delirium, the new TrueFinalBoss. He combines complex bullet patterns with impredictable shapeshifting and erratic TeleportSpam. Add his ''massive'' hp and you have a pretty challenging boss in your hands]].
* CallBack: One of the new items in ''Afterbirth'' is actually an old item: [[http://bindingofisaacrebirth.gamepedia.com/Lusty_Blood Lusty Blood]] is just [[http://bindingofisaac.wikia.com/wiki/Bloody_Lust Bloody Lust as it worked in the original Isaac.]]
* CatScare: The final stage of Greed Mode is named [[spoiler: Ultra Greed]]. At the start of the stage, there's a boss room. You enter it, expecting a hard boss battle...[[spoiler: and then a single Monstro (or a pack of Greeds) appears. Ultra Greed is in the ''[[TrickBoss next]]'' [[YourPrincessIsInAnotherCastle boss room]].]]
* CastFromMoney: The Magic Fingers is an item that instantly deals a small amount of damage to every enemy in the room every time you put a penny into it. It has no cooldown time, so if you have lots of money (or are lucky enough to find the Dollar), you can spam it...until your money runs out, anyway.
* ChestMonster: ''Afterbirth+'' added a chest type that looks normal but becomes spiked when you stand right next to it. After some complaints, the chests were redesigned so that the difference between them and standard brown type was more obvious.
* ClassicCheatCode: Some seeds have interesting effects, such as BRWN SNKE ([[ToiletHumor causes Isaac to leave a trail of poop wherever he goes]]) or [=B00BT00B=], described below.
** Taken even further in ''Afterbirth'', where all those special seeds are now available in a list after you put one in, although the icon that indicates the list seems to indicate an EasterEgg, and can be chosen for any play, as well as removing the ability to progress in unlocks with some. They've all but been named cheatcodes. There is even one that makes Isaac invincible: [[spoiler: [=ALM1=] GHTY]]
* CoolHat: The Host Hat, an item introduced in "Afterbirth". It's a [[ExactlyWhatItSaysOnTheTin Host that Isaac wears on his head]]. It protects Isaac from explosions, and has a chance to block incoming shots and counter with the Hosts' signature three-bullet spread.
* ColorCodedForYourConvenience: Champion enemies have traits based on their suit of color, and all of them do one heart of damage rather than half. Dark green means an enemy [[MadeOfExplodium explodes]] at death and drops a bomb, pale red means [[DamageSpongeBoss massive HP]], dark red means regeneration with a double-heart drop, gray deals double damage and drops a key, light blue means it explodes into bullets on death, green leaves a trail of green creep and drops a pill, and dark blue generally means "less dangerous, but can still hurt you" and gives friendly flies.
* ContractualBossImmunity: [[spoiler:[[TrueFinalBoss Delerium]]]] is the only boss with a single phase that is immune to the Chaos Card. It isn't immune to [[TakingYouWithMe Plan C]], which destroys everything in a room and kills you three seconds later, but its death animation takes longer than three seconds. Only Lazarus or a character with Lazarus' Rags (both of which respawn the player in the same room) can make use of this strategy, limiting any unlocks to Lazarus alone.
* CombinatorialExplosion: Part of the update to the game is that this can now happen. The formula is no longer ''"pick up anything that can help you, hope for Mom's Knife or Brimstone"'' for a win that seems assured; now any number of items can assure victory in combination. Two wildly differing examples are Midas Touch + Book of Shadows + Nine-Volt, which basically gives you the ability to go running around turning enemies into coins every 2 rooms, and Ludovico Technique + magnetic tears + shielded tears, which give you a single controllable projectile that pulls in enemies and shots while disabling all shots that touch it meaning that you have control of basically a black hole against your enemies.
** Another mild game-breaker is homing shots plus Technology 1 or 2. The laser beam actually curves itself around to hit enemies.
** A further combo involves Guppy's Hairball and How To Jump. Jump over enemies to avoid them, and the hairball will plow through them. The momentum will also cause the hairball to bounce about well beyond its normal range.
** And pretty much anything plus Brimstone. Homing Brimstone? (if combined with Spoon Bender) Triple Brimstone? (if combined with Third Eye) ''Ten beams firing simultaneously in all directions''...''[[RuleOfThree Brimstone]]''? (if combined with Tammy's Head).
* CoOpMultiplayer: You can sacrifice one of your hearts to allow another player to create and control a familiar. Some of these familiars have special abilities, and some are unlocked by beating [[spoiler: Mom's Heart]] on Hard Mode.
* CounterAttack: Evil (black) hearts inflict the Necronomicon effect on all enemies in the room when a full black heart is depleted. In fact, ''Rebirth'' includes many items that damage enemies when Isaac takes damage. An example is The Negative, the new counterpart of The Polaroid.
* CursedWithAwesome: One of the random curses that you can get inflicted with is "Curse of the Labyrinth", which essentially merges two floors and forces you to fight two bosses in a row at the end. If you get it on the first floor, both treasure rooms will now be unlocked, sparing you the need for one key. On the other hand, later floors can potentially rob you of an additional Devil/Angel Room that could have spawned for both floors.
* DamageSpongeBoss: While there were already bosses who had this as their gimmick, this is taken to extremes as one of many gimmicks for the two new major bosses of ''Afterbirth'', [[spoiler:Hush and Ultra Greed]], who both have health that eclipses the health of every other boss in the game and even normalize the damage you deal to them, meaning that something that would one-shot every other boss in the game will only deal chip damage to them. ''Afterbirth +'' subverts this with [[spoiler:Ultra Greedier]], who has less health than [[spoiler:Ultra Greed]], yet plays this straight with [[spoiler:Delirium]], who doesn't need normalized damage because he has more HP than even [[spoiler:Hush]].
* DamnYouMuscleMemory: An odd variant--the game's new engine will trick some people up. ''Rebirth's'' new engine is extremely powerful, able to handle insane amounts of stuff on the screen at any time at a rock-solid 60fps even on lower-end video cards, but this has some unfortunate effects on people transitioning from the lower, glitchier framerate of the first. People who are accustomed to the half-second pause when transitioning into a room will routinely screw themselves over on hazards, and attacks are much harder to dodge thanks to a lack of HitboxDissonance.
** Most throwable items are used by pressing the appropriate key and aimed using the keys for firing tears. The Chaos Card, however, is automatically thrown in the direction Isaac's body is facing, meaning that it is aimed by walking in the direction you want to throw the card and ''then'' hitting the "use item" key. Woe betide the player who saves one far a particularly tough boss, forgets how to aim it, and ends up throwing it into the bottom wall.
* DarkerAndEdgier: Even though the regular game is fairly grim on its own, ''Rebirth'' has a much more oppressing and bleak atmosphere, compared to the cartoony and lighthearted (if drenched in BlackComedy) atmosphere of the first.
* DarkIsNotEvil: The Dark Bum, a demonic version of Bum Friend with a description of "He wants to take your life"... meaning he wants to take those red hearts that you can't take because your health is full and turn them into soul hearts (and the occasional spider. Being sick sucks). His usefulness (even after two nerfs) and fairly common appearance rate has pretty much made him an EnsembleDarkHorse, complete with [[https://twitter.com/darkbum Twitter page]].
* DeathDealer: Completely literally with the Chaos Card, which instantly kills ''anything'' it hits when thrown. It can even one-shot bosses! [[spoiler:Except [[TrueFinalBoss Delirium]]. [[NoSell It doesn't work on him.]]]]
* DevelopersForesight:
** The various insects you see--not the enemies you're supposed to kill but the actual pixel-tiny insects that add to the atmosphere--are interactive. Shoot or step on one and they'll turn into small puddles of blood. If you shoot a fly, tiny pixels of blood will fly off and they'll actually spiral downwards to the floor! If you have [[BulletDodgesYou the Soul]], bugs will be steered away from you.
** If you're at half a heart left and you enter a new room, [[PottyFailure Isaac will pee a little at the entrance]] showing how terrified he (and possibly you, the player) is at what dangers this new room may present that could end your run.
** In ''Afterbirth'', the Flush item (which normally [[ContractualBossImmunity has no effect on bosses]]) instantly kills [[TalkingPoo Dingle, Dangle, and Brownie]] when used.
** When you defeat Ultra Greed, he turns into a giant gold statue. Midas's Touch will instantly do this, obliterating his armor reduction.
** In ''Afterbirth +'', Glyph of Balance alters the drops of champion enemies so that you'll get what you need the most. If you're almost dead, its first priority is giving you a red heart - unless you have no heart containers, in which case it'll give you a soul heart instead.
* DifficultButAwesome:
** Anti-Gravity Tears can be very difficult to use, but when used well you can simply drag any enemy that chases you through a path of tears, set traps for enemies that love to jump on your head, and burst down enemies that only expose themselves to damage every so often. Goes UpToEleven with Brimstone: It can be difficult to make every laser hit, but you can now fire full-power Brimstone shots ''as fast as you can charge them''.
** Bob's Brain is notorious for blowing up in people's faces and generally being more trouble than it's worth. However, if you can keep track of its respawn time, keep repositioning so it doesn't immediately blow up in front of you, and LeadTheTarget so it hits what you want, it can function as a high-damage grenade launcher that continually replenishes itself. Particularly skilled users can even time it so that it blows up enemies when they're near bomb-able locations, saving on bombs in the long run. It shows up more frequently than a lot of items, giving players more incentive to learn how to use it properly.
* DownerEnding: The endings added by the expansions make it clear [[spoiler:Isaac thought himself to really be corrupt by sin and was driven to suicide]]. The 20th ending in ''Afterbirth+'' puts everything [[MindScrewdriver more or less into perspective]].
** [[spoiler:Isaac starves and suffocates to death inside the chest while hallucinating the entire game. His mother believes him to be missing and only finds out the truth when there are only bones left inside the chest. We then see Isaac walking into the underworld, followed by a demonic shadow.]]
** The Greed mode's ending features Isaac [[spoiler:getting trapped by a cave-in and becoming Greed after hanging himself. In the Greedier ending, his head then comes off and a fountain of bugs gush out of it. [[GainaxEnding How this fits with the other endings is anyone's guess]]]]...
* DunceCap: The Wiz powerup in ''Afterbirth'' is a dunce cap that gives the player character permanently crossed eyes (similarly to the "r u a wizard" pill).
* DyingDream: [[spoiler:''Afterbith+'' reveals that the whole game is this. Even his mother attempting to kill him was allegedly imagined]].
* EarlyGameHell: The hardest parts of Greed Mode are often the early levels, when you have little health and only average tears and damage. Once you've gained a few items, your chances of survival increase dramatically.
* EldritchAbomination: In ''Afterbirth'', collecting three Devil items transforms you into Leviathan (a mini-Cthulhu), which grants flight and a few extra black hearts.
* EnemyScan: The Spider Mod in ''Afterbirth'' gives every enemy (and segments if applicable) a visible health bar so you can track how much damage they've taken. It also displays how much damage your weapons are doing. Finally, the spider familiar itself wanders around randomly and can cause random effects to any enemy that touches it.
* EscortMission:
** Isaac's Heart makes Isaac immune to damage, but generates a heart familiar which takes damage in his place. Enemies will target the heart instead of Isaac, so it has to be protected. On the plus side, Isaac can use any self-damage item for free.
** The Guardian challenge gives you a character with invincibility, flight and a powerful sword to stab monsters with. The catch? You must protect a Punching Bag with Isaac's Heart attached to it. The Punching Bag takes damage, not the heart, and you have no control over how the Punching Bag behaves. You have to escort him all the way to Womb II. Most of the time, [[LuckBasedMission it is impossible]] to prevent the dude from getting hit a handful of times, though at least it tries to avoid traps in rooms. Usually. It's especially bad when you end up with charger-type bosses that can't be knocked off course, which means the Punching Bag is guaranteed to take hits.
* ExactWords: The Suicide King card's description is "A true ending." FromACertainPointOfView, it does just that, since [[spoiler: it drops several items then kills you.]]
* {{Feelies}}: The ''Nintendo Switch'' boxed release includes a fully illustrated instruction manual, which parodies the original ''Legend of Zelda'' game manual, as well as some stickers featuring some of the game's character's and enemies.
* FireWaterJuxtaposition: The new alternate chapters for the Basement and the Caves in ''Afterbirth'', Burning Basement and Flooded Caves.
* GameBreakingBug:
** There seems to be a game crashing bug that crashes the game when enough damage is done to [[spoiler: Mega Satan]] that they die without changing forms. It's rare, but it appears to be very consistent.
** Sad Bombs give bombs a Tammy's Head effect. [[spoiler:Godhead adds a giant halo to each tear.]] There's a glitch that allows one to let loose as many bombs as the screen will handle. Combining all three is the only way outside of [[spoiler:Mega Satan]] to crash the game.
** In ''Afterbirth'', Ending 17 is supposed to be unlocked by defeating [[spoiler:Hush]] at ???, but it only works once. On replays the player receives the exits to the next chapter instead. The problem back when the expansion was released is that imported saves from ''Rebirth'' wouldn't get the ending chest if they already had Chapter 5 unlocked. Trying to enter ??? as some characters would always crash the game, too.
** Alluded to by the ''Afterbirth'' item GB Bug, which has the description "Game breaking bug, right away!" It adds a "glitchy" familiar that bounces around the room inflicting random status effects on enemies.
** [[spoiler:Delirium]] is meant to be completely immune to the Chaos Card but when it gain multiple hitboxes it becomes vulnerable. Which isn't supposed to happen and the game crashes. Time to hope you brought good items.
* GameplayAndStoryIntegration: One of the new rooms is a bedroom where Isaac can sleep in a bed to recover health. In the center of the room, there is a rug. [[spoiler: Blow it up with a bomb to reveal a hatch to the next floor or a crawlspace. You may want to rewatch the intro at this point.]]
* GlassCannon: ''Afterbirth'' added a ''literal'' Glass Cannon, which grants a powerful, reusable shot but also reduces Issac's health to just half a heart. A patch nerfed it hard so it takes away all three kinds of hearts.
* GlassWeapon: In ''Afterbirth'' you can create the Glass Cannon, which is exactly what it sounds like, in [[GlassCannon every sense]]. It's incredibly powerful, but lowers your health to just 1/2 heart, meaning that you'll be killed in a single blow if something hits you.
* GuideDangIt:
** Unlocking [[spoiler:the Lost]] would be a tall order for any one player to accomplish using only the resources made available in game, so much so that the process was ultimately figured out by some people data mining and spoiling it; this unsurprisingly prompted an upset response from creators Edmund [=McMillen=] and Tyrone Rodriguez, who noted it was meant to prompt an [[AlternateRealityGame ARG]]-type response with the community working and speculating to solve it. The process was meant to be a community effort, which probably would have worked eventually, but it is still fairly obscure. You either need to spend a long time going in circles and following vague clues to figure this out, though it should be noted that knowing what to do isn't [[SelfImposedChallenge half]] [[MoonLogicPuzzle of]] [[NintendoHard it.]] [[note]]To put it in perspective, the process involves dying in a certain room holding a certain item in order to receive one part of four images that hint at the actual unlock process, which involves dying with four certain characters in certain locations under certain circumstances in a certain order. ''Consecutively''.[[/note]] The unlock method has been significantly shortened (but made more luck-based) in ''Afterbirth'': [[spoiler: Die with any character in a Sacrifice Room, while holding the Missing Poster. The difficulty is now getting both items to appear in a run, since seeded runs do not work.]] However once you unlock them, you can use them in any run afterwards.
** Two stats are not shown on the stats screen, or elaborated upon at all. You have "Evil / Faith", which is a sliding scale determining what kind of special deal (Deal With The Devil or Deal With The Angel) you get when you qualify for one, and Shot Height, which is used as an alternative to range in some items that claim to increase it (notably increasing Shot Height as Azazel is a ''bad thing'' and makes his range ''shorter'').
** Different damage upgrades are "worth more" than others. Furthermore, some simply add to your damage stat (Damage +1 for instance), while others give you a multiplier instead, or on top of, adding to it, which is significantly better most of the time. The highest of both types are provided by, respectively, Ipecac (+40 damage) and Tough Love (3.2 damage multiplier for each tooth.)
** Special items are back! Not only was this completely unexpected due to Edmund outright saying they would be removed, they now work differently. Instead of the huge list of Special items from the original, there are now only fifteen: [[spoiler:Polyphemus, Mutant Spider, Brimstone, Sacred Heart, Soy Milk (no longer Special in ''Afterbirth''), Pyromaniac, Lil Brimstone, Ludovico Technique, Dr. Fetus, Epic Fetus, the D6, Mom's Knife, Stop Watch, the D100, and Godhead]]. What's more, the Special counter is changed based on sight, not pickup, meaning seeing some of the bad Special items will make it less likely you'll get good ones.
** Lazarus' entire playstyle is bizarre. He starts with a negative Luck stat (-1), and greatly benefits from ''dying'' as early on in the run as possible, since the item he starts with (Lazarus' Rags) give him a damage bonus when he revives.
** Unlocking the Blinding Baby requires you to use The Sun card via the Blank Card activated item. Either you get this one by accident or never figure it out on your own.
* HitboxDissonance:
** The wall-crawling spider type enemies have a damage hitbox that's extremely confusing, placed at least an inch away from the front of the actual model. Since this hasn't been fixed and the crawlers are often protected by a pit, this could be intentional to keep the game from becoming unwinnable by having extremely low range. Still, this can be frustrating when Brimstone and diagonal shots like tiny planet don't hurt them despite visibly touching them.
** This can happen to Isaac himself through size-altering pills. "One Makes You Larger" does ''not'' increase the size of Isaac's hitbox, but it does increase his visual size. "One Makes You Small" ''does'' decrease Isaac's hitbox along with his size.
* InstantRunes: The Black Powder in ''Afterbirth'' causes a trail of black powder to appear where you walk, which dissipates after a certain distance. Forming a circle with the powder forms a glowing red pentagram which damages any enemy that touches it.
* InterestingSituationDuel: The "Challenges" give you certain combinations of items that can drastically alter the way you play. For example, the "When Life Gives You Lemons" challenge mentioned below gives you Lemon Mishap (a JokeItem) and lowers your stats, but also gives you the Nun's Habit, Nine-Volt and a single Lemon Party pill. Since your stats are so bad, you'll have to rely on leading enemies into the damaging puddle dropped by Lemon Mishap until you get better items (but due to the Habit and Nine-Volt, you can use the Lemon Mishap in almost every room, more often if you take damage).
* InterfaceScrew: This game adds three new interfaces curses on top of Curse of the Lost (minimap disabled). Curse of the Unknown removes your health bar, forcing you to keep a mental tally. Curse of Darkness reduces the ambient lightning to almost nothing, though the player and most enemies glow. Curse of the Blind turns every pedestal item (activated and passive items) on the floor into a question mark, including Devil/Angel Room items and shop inventory. It'll make you think twice about picking something up.
* JackOfAllStats: Invoked by the Libra item, which actively balances your stats once you collect it. Can turn the player into a MasterOfNone or MasterOfAll, depending on what items it is mixed with.
* JumpScare: [[spoiler:Ending 3 a.k.a. The Rubber Cement ending.]]
* KaizoTrap:
** Mom's Heart now explodes into a radial bullet burst when killed. It's easy enough to dodge if you know it's coming, but a surprise nonetheless.
** Devil Rooms in ''Afterbirth'' have a chance to contain enemies that you have to kill in order to leave.
* LastLousyPoint:
** ''Rebirth'' is much worse about this than the original, especially with Secret Room items. Since the Secret Room is less likely to spawn items combined with more possible variations, most players resort to exploiting the item pool mechanics to reroll Secret Room items from Beggar drops or mushroom spawns. Another annoying item is Steven, which is now impossible to find except by killing Steven in a main boss fight (already rare to begin with), and only has a 1 in 5 chance of spawning compared to Little Steven. Rerolling also doesn't work on Steven drops, so it has to drop normally.
** Applies much less in Afterbirth: Greed Mode's restocking shops mechanic and expanded shop item pool means it is possible to see the secret room items there. As for Steven, it now drops in Golden Chests.
* LethalJokeWeapon: Because of the improved item synergies, many mediocre items can become the keystone to a weird yet highly effective setup. Bonus points if several if your items are bad but [[AllYourPowersCombined they become effective in tandem with each other.]]
** Lemon Mishap and Pinking Shears, two mediocre-at-best items in ''Wrath of the Lamb'', have been buffed to the point that they can singlehandedly kill bosses.
** "A Card Against Humanity". You'd be surprised at how badly some bosses handle a room full of poop. Becomes even better if you can remotely attack through Ludovico Technique, ???'s Only Friend, or Robo-Baby 2.0.
* LongSongShortScene: The [[spoiler:Blue Womb[=/=]???]] area gets a dang nice song, even though it is simply a single room before a boss fight.
* LuckBasedMission:
** Eden is entirely built around this trope, starting with random stats and items. However, using them requires "tokens", which are acquired by defeating Mom. This is to prevent SaveScumming for a set of good items, though it's easy enough to earn a large surplus if you use other characters consistently.
** "Dice Rooms" are rare rooms with [[ShapedLikeItself a giant die on the floor]]. Stepping on it may re-roll Isaac's items, reroll the pedestal items on the current floor, reroll the pickup items on the current floor, ''restart'' the current floor, or ''several of the above at once''. Using such a room can be the ultimate gamble.
* TheLoad: Familiars have the potential to screw you over to an even greater degree than before, especially when "free-roaming" and "explosives" are dangerously mixed. Special mention goes to the BBF (essentially a friendly Boom Fly) which combines ''both'' and is liable to blow up in your face if the enemy it collides with happens to be near you.
* LuckilyMyShieldWillProtectMe: The Trinity Shield blocks all bullet attacks from Isaac's front, moving with Isaac.
* MagikarpPower:
** One of the new ideas added to the game is the possibility of crippling yourself by picking up a bad item early, Tiny Planet and Bob's Brain to name two, in the hopes that later in the run you'll pick up an item that goes complements them really well, a high attack speed or piercing shots for tiny planet making it better than the pretty inaccurate item it is normally. One could argue it's part of what makes the game more fun than before, just the pure number of items that you might pick up and hold on to in the hopes they work exponentially well with another item you find on the run.
** The Void item added in ''Afterbirth+'' has two properties. This first, which is moderately useful, allows it to destroy any passive items in a room and covert them into random stat boosts, with a chance for a slight range reduction. The second, which applies to this trope, allows it to destroy any spacebar items and permanently copy their effects. There is no limit to how many items can be absorbed this way, and all of them will trigger each time Void is used. This can include generating Soul Hearts, Black Hearts, Eternal Hearts, mapping a floor, using Blank Card and its combos, Placebo and its combos (most importantly, '''infinite charge'''), four-way Brimstone from Krampus, and so forth. The only things it can't copy are spacebar items that are consumed upon use.
** Also in ''Afterbirth+'', the Smelter item. It takes 6 rooms to charge, and each use removes Trinket(s) and permanently applies its effect to Isaac. If you happen to find Mom's Box or a Fortune Teller machine, you'll quickly become unstoppable.
* MarathonLevel: The new VeryDefinitelyFinalDungeon, [[spoiler:the Void]], is this. It's as large as two XL Womb floors put together and has 6 or 7 boss rooms besides the FinalBoss fight, one of which always contains another "final" boss. Good luck finding your way there if you get hit by Curse of the Lost.
* MurderSuicide: [[InvokedTrope Invoked]] by a new item in ''Afterbirth +'', the Plan C. It instantly kills ''anything'' in the room (even final bosses)... and kills you shortly afterwards.
* MusicIsEighthNotes: The Dingle boss whistles to summon mooks. The audio is accompanied visually by a few eighth notes.
[[/folder]]

[[folder:N-Z]]
* {{Nerf}}: An inevitable result of re-balancing the game from ''Wrath of the Lamb'', several items and one character (Cain) were weakened for balancing purposes. On the flipside, Samson received a much-needed buff.
** The Bloody Lust mechanic change to powering from Samson taking hits instead of getting kills is a significant change of strategy for the worse due to his starting health.
** An ''Afterbirth'' patch nerfed Lilith's Box of Friends and Azazel's Mini Brimstone laser's power and charge time. Another patch un-nerfed Azazel's damage, but made his charge time ''worse''.
** ''Afterbirth'' also nerfed Judas's Book of Belial to only increase the chance of getting a Devil/Angel Room when held instead of guaranteeing one whenever possible.
** A patch for ''Afterbirth'' made a very controversial nerf to the [[PurposefullyOverpowered Stopwatch]]. Instead of having it slow down every enemy permanently, it was changed to activate only after taking damage ''and'' having its effect only last for one room. Many people were visibly upset by this, and in a later patch, while it kept its flaws, it was changed to [[ObviousRulePatch also activate if Holy Mantle's shield was broken]], which at least still makes it a very useful item when playing as [[spoiler:The Lost]].
* NewGamePlus: In ''Afterbirth +'', if you defeat the Lamb as your FinalBoss, you're given the option to do a "Victory Lap". You start from the first level with all your items intact. This can be done endlessly, and the game tracks how many times you repeat. Most achievements won't work in this mode (only the "U Broke It!" achievement can be earned on a Victory Lap). Further, on the third victory lap, the game increases in difficulty (you are turned into [[spoiler:the Lost]], minus his Holy Mantle and D4, and shops no longer appear).
* NiceHat: ''Afterbirth'' introduces the item Host Hat, which puts a Host on Isaac's head. The item's in-game description is even "Nice hat!"
* NintendoHard: A "hard" difficulty level has been added, which significantly dials up the amount of enemies and [[EliteMook champions]] while giving you less powerful items. ''Afterbirth+'' does this for Greed Mode, which is called Greedier Mode.
* NoFairCheating: Level seeds allow you to repeat a powerful run, but block any achievements. Similarly, challenge maps only allow you to unlock the associated achievement. Finally, the NewGamePlus blocks any achievements.
* NotTheIntendedUse:
** The [[spoiler:key pieces from the Angels]] are supposed to be used to unlock the TrueFinalBoss. However, if the player's objective is the regular boss of that floor, then these items can be rerolled with the D6, allowing for an extra Angel Room item. Players can also bet on getting Dad's Key later to sidestep the problem, but this is less likely.
** Also, Dead Cat (which gives you nine lives...at the cost of only having a single heart container for each life) can be used to purchase every Devil Room item for basically free: you pay for the Devil Room item with your last heart, you die, you get resurrected, you go back into the Devil Room, pick up the other Devil Room item, die again, get resurrected again, continue to the next floor with 7 lives remaining and two free items! If you're good at dodging, you probably don't need all nine lives anyway.
* OneHitKill: The Chaos Card kills almost anything in one hit. The only things that can survive it are [[spoiler:the first form of Satan, the first form of Mega Satan, Delirium ([[ContractualBossImmunity which is the only intentional exception]])]], and, likely due to a bug, Scolex.
** Plan C takes it a step further by [[SmartBomb instantly killing everything in the room]]. [[spoiler:Including Isaac.]]
* PajamaCladHero: The PJs ''"make you feel cozy"'', which shows by healing Isaac to full health and giving him four extra soul hearts on top of that.
* PowerUpLetdown:
** The general opinion of Bob's Brain. It's a minion/follower that charges into enemies in a straight line when "fired" along with Isaac's tears, exploding on contact. It will do this even if the enemy is right next to Isaac, causing him to take SplashDamage. It also doesn't explode on the return trip if it misses, making it hard to aim, and doesn't synchronize well with tears. BBF (Big Beautiful Fly) also falls into this category for exploding upon contact with enemies (regardless of location) though at least BBF's movement is predictable and can be accounted for.
** Thought that Samson or [[spoiler:???]] wasn't worth the effort in the original? The crappy reward-to-effort ratio for [[spoiler: The Lost]], a genuine JokeCharacter, is even ''worse''.
** The Suicide King special tarot card requires beating one of the more infuriating challenges to unlock and has the splendid effect of dropping 10 items... and killing you.
** The Lord of the Flies transformation gives you flight, and makes all enemy flies into friendly blue flies. That's about it... At least it's free flight, but Guppy is far superior.
** The new transformations in ''Afterbirth'' range from helpful to nearly pointless. The Mushroom, for example, is just a free Health Up.
** Tiny Planet, which makes your shots orbit you at a fixed distance instead of going forward... which makes it almost impossible to hit anything with more than half your shots, forces you to fight at close range, and makes knockback useless for defense. At least it works differently with a few alternate attacks (notably Brimstone).
** Curse of the Tower, unless you have an item that provides bomb immunity or invincibility after being hit. It spawns a handful of troll bombs any time you take damage, dealing lots of damage to anything in the room--but possibly also damaging you again. And it will destroy any blood donation machines or demon beggars you try to use.
** If you manage to defeat one of the hardest bosses in the game with the Keeper, one of the hardest characters in the game, you are rewarded with... him starting with a single penny in future runs. Gee, thanks.
** The Wiz allows Isaac to shoot tears out of both eyes at once, but also forces him to shoot diagonally (effectively a permanent "R U A Wizard" effect). Given that the game is designed around shooting in the cardinal directions, it's generally more of a hassle than a benefit.
* PromotedToPlayable: Some of the hidden items from the original game are now unlocked from the start in ''Rebirth''. Other items now have different unlock requirements, such as The Nail. And inverted with a few items that didn't need to be unlocked in vanilla, such as the Wire Coat Hanger.
* PurposelyOverpowered:
** The Stopwatch. Unlocking it requires you to put 999 coins in the Donation Machine (which can take dozens of runs since the Donation Machine will randomly jam and refuse further donations for that run). Once you have it, it slows down all enemies and their bullets for the duration of that run, making it a near-cakewalk. It got hit with a huge nerf in ''Afterbirth'' via a patch, reducing it to an on-hit, single room effect (still pretty good against bosses, but not quite as useful overall).
** The Mega Blast is Brimstone or Krampus' Head on crack. It gives you Mega Satan's giant Brimstone laser, which lasts a solid 15 seconds and persists between rooms, allowing you to steamroll through numerous rooms before the laser runs out. However, this requires beating [[spoiler:[[HarderThanHard Mega Satan]]]] with every character, including the JokeCharacter AND it's the only item in the game with a 12-room charge (and batteries only refill 25% of the charge bar), so you'll only be able to use it once every two floors, or once a floor if you're lucky. With the addition of Void in ''Afterbirth +'', you can even bypass the long charge time.
** Mama Mega! is this. When used, it deals kills every normal enemy in a room (if an enemy spawns another upon death, you have to kill them yourself), does massive damage to bosses, destroys all forms of rocks (but not Keepers or rocky chests), opens all Secret and Super Secret Rooms, and even opens the paths to Boss Rush and the Blue Womb if you've passed the time limit for either. Best of all, it lasts for the entire floor on which it is used. It basically gives you an entire "free" floor with nothing standing in your way.
* RecurringBoss:
** Depending on your choices and luck, you may fight The Fallen as a boss four times in a single run: once at a random level, once during the boss rush, once as a Double boss in the Womb, and once guarding Satan. Not counting the times it shows up as a regular room enemy and its slight recoloring Krampus.
** Similarly, the Greed/Super Greed battle is almost guaranteed to replace one of the shop rooms or secret rooms you've striven to unlock. Bonus points if the two show up on consecutive floors. He's so common, that a trinket, [[spoiler:Greed's Rib]], added in ''Afterbirth'', prevents any form of Greed from appearing.
** There are four completely different Gurdy bosses for various stages in her life cycle, which can be fought in each of the four main areas of the game. You can potentially fight them all in one run.
** In Greed mode, you are naturally quite likely to fight several copies of Greed and/or Super Greed on the penultimate level, then fight several more copies at the beginning of the final level. And then you fight Ultra Greed.
* {{Retraux}}: ''Rebirth'''s art style is intended to resemble a colorized Gameboy game. Additionally, there is an arcade filter available by using the [=B00BT00B=] seed code. ''Afterbirth'' adds a Retro Vision pill which pixelates the screen on and off for a minute or so.
* RockMeAsmodeus: ''Hericide'', [[spoiler:Satan]]'s new boss theme.
* SaveScumming: Intentionally discouraged with the increased item synergies in the hopes that players stop immediately restarting when they get a bad item early on. Then again, the seeding tools provide for a form of this if one gets particularly lucky with their game's generation and want to retry after dying partway through.
** Also discouraged with Eden. Eden starts with random stats and items, so selecting Eden requires and consumes an Eden Token gained by beating end-game bosses. But if you're a good enough Isaac player you'll have more Eden Tokens than you know what to do with.
** By forcing the game to quit before the Game Over screen comes up you can reload your last suspend save, but never collect Guppy's Collar while doing this. The game forces 1-up effects when you save scum and the Collar works by either reviving or killing you.
** ''Afterbirth +'' punishes repeated resets with the Mr. Resetti achievement: it unlocks [[PowerUpLetDown half soul hearts]] for the next runs.
* SchmuckBait: There's an unlockable tarot card called [[spoiler:Suicide King.]] Upside, it spawns a bunch of cool pickups. Downside? [[spoiler:[[ExactlyWhatItSaysOnTheTin You die]]]].
* SecretCharacter: A new one for this version. [[spoiler:"The Lost", a OneHitPointWonder incapable of gaining [[OneHitPointWonder any hearts]] and starts with flight.]] Unlocking him is a real GuideDangIt: the old way was to [[spoiler:die to Mullibooms as Isaac on the basement, then to your own bombs as Maggie in the caves, then to Mom as Judas, then to Satan stage 2 as Azazel, with no deaths in-between and in that order.]] In ''Afterbirth'', you just have to [[spoiler:kill yourself in the Sacrifice Room with the Missing Poster in your inventory]].
** Another one was added in ''Afterbirth'': [[spoiler:The Keeper. He uses coins for health and converts all hearts into blue flies. He can only have up to 2 coins worth of health at a time, yet while he can't gain any, he can still ''lose'' them. On top of that, he's slow and fires triple shots at reduced speed.]]
* SequelDifficultySpike:
** Zig-Zagged. ''Rebirth'' adds a lot of new content while updating older items from the original, which makes things both more difficult and easier thanks to the new items but larger item pool. The shop gets a major revamp with a lot of very useful items to potentially buy. The main bosses are a straight example, all of them having been given new moves and BulletHell abilities which make the fights twice as hard as they were in the original game.
** The ''Afterbirth'' expansion adds new features to the level design such as cramped rooms and trap rooms. Multiple bosses at cramped rooms don't mix well. And certain trap rooms only give you a split second to react before a bomb explodes in your face. There are also trapped treasure rooms which might require you to use a bomb to reach the item.
* SillinessSwitch: Some special seeds you can type in have strange and sometimes hilarious effects. For example, FART SNDS turns all sound effects in the game into, you guessed it, fart sounds. Find a nickel? ''Pffrt''. Open a door? ''Ffrrp''. Take damage? ''Prpfff''. Another good one is SLOW 4ME2, which increases or decreases the background music tempo depending on how fast you're moving.
** As of ''Afterbirth'', inputting a special seed permanently unlocks its effect, and ''any number'' can be toggled in a new [[EasterEgg menu of Easter Eggs.]][[labelnote:Spoiler]]Press Q (or LB) on the character select screen.[[/labelnote]]
* SolidGoldPoop: In ''Rebirth'', any run-of-the-mill poop piles you find have a chance to be golden poop piles, which drop a bunch of coins or the Counterfit Coin trinket when destroyed. [[spoiler:Having The Poop active item and Midas' Touch will let you spawn these every single room.]]
* SpeedRun:
** Now actively encouraged, since many features were added to help out the dedicated SpeedRun community. All runs have an internal timer attached to them (viewable by pulling up the map, which also displays the current level for screenshot purposes) and the game keeps track of your best times for fresh runs as each character (i.e. randomly generated, not from a seed). The main purpose of seeds was to allow for many people to play the same run and compare completion times, since without seeds the times were too often influenced by the RandomNumberGod. There are now leaderboards for the quickest runs for a particular daily seed and [[SeriousBusiness competitive speed-running]] may very well arise.
** Additionally, beating Mom in under 20 minutes grants access to the special BossRush room. The little clock that's visible during each loading screen shows how much time is left until this room expires, and you can bring up the map to check your current time.
** The Speed! challenge requires you to beat It Lives in 16 minutes, or every 10 seconds you take a half-heart of damage. On top of that, all enemies and their bullets move twice as fast.
** In ''Afterbirth'', defeating Mom's Heart/It Lives in under 30 minutes grants access to [[spoiler:The Blue Womb and the BonusBoss Hush]].
** In ''Afterbirth+'', one achievement (and a new item) can only be unlocked by beating the Lamb in under 20 minutes. [[ThatOneAchievement Good luck with that.]]
* SpreadShot: Where to start? Several enemies use these, and there are ''many'' items that allow the player to fire in spreads.
* StandardStatusEffects: The Iron Bar item adds a Concussion tear effect, which confuses enemies. The Charm tear effect causes enemies to actively seek out and damage other enemies, if they are capable of doing so (enemies stuck on a certain path, such as rolling guts, don't seek out other enemies); the charmed enemy can still damage you, however. The Fear tear effect causes enemies to slowly run away from you, and stops some enemies from firing at you. The Fire tear effect deals some brief continuous damage after hitting an enemy, and causes occasional fiery explosions. The Slow and Poison effects return from the original game. They're unchanged except affected enemies now have an icon above their heads.
* StealthPun: The Latchkey gives you [[LockAndKeyPuzzle Luck and Keys]].
* {{Stonewall}}: One of the new items, Punching Bag, gives you a friendly Mulligan that acts as a tank for you.
* StuckItems: You're still stuck with whatever is held in your use slot like in the first game until you find another usable item. However, it's thankfully averted with pills, trinkets and tarot cards, which can be dropped by holding down the map button (or the left Ctrl button on your keyboard). But even the map button cannot get rid of the Tick trinket, which is the one truly irremovable item in the game.
* SuperPrototype: Technology 0.5 is a far superior laser when compared to Technology and Technology 2. It doesn't replace your regular tears so is a direct firepower upgrade when you pick it up, doesn't have a damage multiplier reduction built into its stats and perfectly synergizes with your power-ups. It also randomly adds power-up effects. Its only downside is that it occasionally misfires, but you'll barely even notice it.
* SuspiciousVideoGameGenerosity: The item pool got buffed ''again'' from ''Wrath of the Lamb'' by introducing items that confer benefits worth two separate items from "Vanilla" ''Isaac''. You'll need those buffs for sure...
* TalkingPoo: The Dingle boss, and his minions (Squirts).
** ''Afterbirth'' adds [[PaletteSwap Dangle]] and Brownie.
* ThemeNaming: The {{Disc One Final Boss}}es [[spoiler:and ''Rebirth''[='=]s True Final Boss]] all have boss themes that end in ''cide''. (''Matricide'', [[spoiler:''Ventricide'', ''Hericide'', and ''Infanticide''.]] Averted with the [[spoiler:fake]] {{True Final Boss}}es, who have uniquely named themes ([[spoiler:''Ascension'' and ''The Fallen Angel'']])
* ThiefBag: In ''Afterbirth'', money bags will occasionally spawn that drop a few bombs, coins, or keys when grabbed.
* TooAwesomeToUse:
** The Friendly Ball allows you to "capture" an enemy and release it to fight with you until it dies, persisting between rooms and floors. However, since the item has a 4-room recharge, it can take at least eight rooms in order to successfully release an enemy you captured, and even then your new companion will most likely die after a couple rooms.
** Mega Blast is an activated item which fires a massive Brimstone laser which does insane damage and persists between rooms and floors, lasting for fifteen seconds. However, not only does it have a 12-room recharge (the only item in the game to require that many rooms), but the battery pickup will not fully recharge the item for another go. Because of this, Mega Blast tends to be saved for endgame floors/bosses that players want to wipe out quickly, such as the [[DamageSpongeBoss insanely tanky]] BonusBoss.
** The Chaos Card can OneHitKill ''literally anything'' in the game. The catch, of course, is that it's a card and can therefore only be used once. Like Mega Blast above, the Chaos Card tends to be saved for endgame bosses such as said insanely tanky BonusBoss. Unless, of course, the player gets a Blank Card...
** Diplopia is an activated item that doubles every pickup and collectible item in the room. With the number of items in the game that stack with themselves, this can create some insane synergies. However, it's only good once, and you can't cheat by using the ? Card to duplicate its effect because doing so consumes Diplopia anyway for no additional benefit. It often comes down to a decision regarding whether to use it on the decent item you have in front of you, or to hold onto it in hopes of getting a better item to duplicate later on.
* TookALevelInBadass: A number of characters, playable and otherwise:
** Mom's Heart/It Lives was a rather straightforward FlunkyBoss in the original game. This time around... let's just say that BulletHell veterans will feel right at home.
** [[spoiler:Isaac/???]] likewise get a bullet hell buff and new attacks.
*** Isaac's third form is [[InvertedTrope considerably easier]] in Rebirth - his light attacks are easy enough to avoid as you can guess the pattern of the safe zones, plus his bullet hell attack has a much shorter range, is easier to dodge and is not homing. And he doesn't spawn angels in this phase.
** Eve has more health and Whore of Babylon kicks in at one full heart instead of a half, allowing her to take advantage of the serious damage buff while still being able to endure a blow from most early game enemies, giving her a chance to build up a buffer of spirit hearts.
** Samson has much more health, increases damage done for every hit he takes, has much larger range, and keeps accrued bonuses across the entire ''floor'' instead of just the room.
** Most characters receive an upgrade to their starting load out once certain conditions are met. Such as Cain starting with the Paper Clip (unlocks Gold Chest for free) or Eve starting with the Razor Blade (boost damage for the room at the cost of a heart, letter her trigger Whore of Babylon at will).
* TrueFinalBoss: Attempts always end after a certain boss, though unlocking more stuff and meeting certain requirements can result in the bar being raised on who is considered the final boss; for example, the very first run ends with Mom at stage six, though beating her a second time spawns the door to the next stage, where players have to fight the new final boss, [[spoiler:Mom's Heart]]. Assuming everything is done perfectly, you have to reach the credits ''eighteen'' times to unlock TheVeryDefinitelyFinalDungeon and face the [[spoiler:8]]th final boss.[[labelnote:exp.(spoilers!)]]First run ends at Mom, unlocks Womb; eleven runs to unlock It Lives! and Cathedral/Sheol access; five runs to kill Isaac/Satan to unlock The Chest/The Darkroom access; one run to kill either ???/The Lamb and spawn the Golden Gate.[[/labelnote]]
** However, with a bit of SequenceBreaking using [[spoiler:a Devil Room that spawns after the Mom's Heart fight, which always leads to Sheol even if you haven't yet unlocked It Lives!]], one can theoretically reduce this to eight runs[[labelnote:exp.(spoilers!)]]1 run to unlock the Womb, 1 run with the Devil Room to defeat Satan (and unlock Judas, whose starting item guarantees a Devil Room will spawn whenever possible), 5 more runs to unlock the Negative, 1 run to defeat the Lamb and unlock the Golden Door.[[/labelnote]]. Still quite a few runs though.
** In ''Afterbirth '' there is the True ''True'' Final Boss in the [[TheVeryDefinitelyFinalDungeon Truly Final Dungeon]], [[spoiler: Delirium]].
* UnexpectedGameplayChange: Some challenges take away your tears completely and force you to fight with either attack familiars or a recharging spacebar item and maxed bombs.
* UniqueEnemy:
** There's a blue-skinned variation of the Conjoined Fatty monster that has a very slight chance of appearing in the I AM ERROR room and [[spoiler:the Chest]]. Despite what its appearance may imply, it's completely distinct from a champion variant and attacks with vicious homing Ipecac shots.
** The bosses [[spoiler:Hush]] and [[spoiler:Ultra Greed]] spawn Gapers that are reskinned to fit the respective boss's motif. [[spoiler:Hush]] also spawns uniquely-skinned Ring Flies that form more complex formations than the normal variety and reskinned Boils with a different attack pattern.
** Two Stone Grimace varieties are extremely rare and only appear in one floor. One is the Broken Gaping Maw, which alternates between trying to suck the player character in with more force than the normal Gaping Maws and not doing anything, found only in [[spoiler:the Womb]] and neither of its alternate floors. The other is the Brimstone Grimace, which fires brimstone lasers and can only be found in [[spoiler:Sheol]]. It is possible to play the game for a long time through several runs without even seeing either of them.
* UnwinnableByMistake: The Blue Bomber challenge turns off your tears but gives you the Kamikaze spacebar item and Pyromaniac (immunity to bombs). Some enemies, however, are immune to Kamikaze, so you need bombs or another source of damage to kill them. If you have neither, you have to reset. Mercifully, a patch added [[CherryTapping Brother Bobby]] to the player's arsenal, which prevents the situation from being ''completely'' unwinnable.
* UpToEleven: ''Afterbirth'' has the XXXXXXXXL challenge, which is the "XL" level effect on steroids. All levels have a size which is roughly equal to an XL Womb level.
* VariableMix: If the room has a lot of enemies or there's a miniboss, an electric guitar harmony fades into the music.
* ViolationOfCommonSense: With a hard cap of 12 hearts compared to the original having no cap at all, it's actually to your benefit to only have a few red hearts. Having full health means you will be unable to pick up spirit hearts or the new black hearts (which deal full room damage when depleted, similar to the Death tarot card). This means runs in which a low number of health containers are found may actually be more viable. It also seems that spirit hearts are a bit more common, and black hearts are more likely to pop up than you might expect for something so useful.
* WesternZodiac: The 12 signs of the zodiac appear as upgrades for Isaac.
** Aries increases speed and lets you deal damage to enemies by running at them.
** Taurus slows the player down, but when in a room full of enemies you build up speed over time, eventually getting the My Little Unicorn effect.
** Gemini gives Isaac a little buddy attached to him that attacks enemies when they get close.
** Cancer gives 3 soul hearts and makes all damage reduced to 1/2 a heart when he takes damage in a room.
** Leo allows the player to break rocks, mushrooms, skulls, etc. by stepping on them.
** Virgo has a chance to make the player invincible after taking damage and makes all negative pills positive.
** Libra balances the player's stats and gives 6 coins, bombs, and keys.
** Scorpio gives the player's tears poison effects.
** Sagittarius makes the player's tears penetrate enemies and increases speed.
** Capricorn increases all stats.
** Aquarius leaves a trail of tears behind the player, damaging enemies that step in it.
** Pisces increases tear fire rate and the amount of knockback enemies take from tears.
** Finally, the Zodiac item takes the effect of a random zodiac sign every floor.
* WhamEpisode:
** The 15th and 16th ending. [[spoiler: Respectively, Isaac is shown to have gone missing, with his mom searching for him, and Isaac turns into a demon!]]
** Ending 17 and 18. [[spoiler:The first confirms Isaac died trapped inside the chest. The latter is another take on his death: he's crushed by debris while trapped on some cave and his corpse becomes Greed.]]
** Ending 20. [[spoiler:His mother trying to kill him was imagined. Isaac killed himself by locking himself up in the chest because he blamed himself for his family falling apart, thinking that he was corrupted by sin]].
* WingedSoulFliesOffAtDeath: The new death animation. [[spoiler: And it's a top secret character, called "The Lost"!]]
* AWinnerIsYou: Inserting coins into the Greed Donation Machine grants you a few unlocks for the first hundred or so. Originally, it stopped at around 109, but a patch allowed the player to set the donations towards 999, which does nothing but praise the player with fireworks at the end and award an achievement. [[spoiler:But something major happens if you donate one more coin...]]
* WhenLifeGivesYouLemons: The name of Challenge #12.
* WorldOfSymbolism: ''Isaac'' explores the same themes as most of Edmund [=McMillen=]'s older games, such as ''VideoGame/TimeFcuk'', but uses very different imagery to do so.
* WrapAround: The Continuum item grants this effect to your tears, causing them to pass through walls and emerge from the opposite side.
[[/folder]]
----
-> [[TheStinger Dear Diary]],
-> [[TvTropesWillRuinYourLife Today I died]]. I was killed by this page on [[Wiki/TVTropes some wiki]]. (ugly)
-> I leave all that I own to my pet cat Guppy. (Pretty cool stuff!)
-> Goodbye cruel world,
-> -XOXO Troper
----

to:

* ArcNumber: 109, the number of coins originally supported by the Greed donation box. The developers teased players about it and misled them into a wild goose chase for secrets, but what it meant is that a certain amount of content was simply blocked off until a patch came out after 109 hours. Coincidentally, 109 also happens to be the in-game ID of the item Money = Power. 109 is also the pickup quote for the Dataminer active item in Afterbirth +.
* AsTheGoodBookSays: ''Rebirth'''s theme is titled Genesis 22:10. The verse? "Then he reached out his hand and took the knife to slay his son."
* TheArtifact: The starting room still displays the Move, Attack, Bomb, Item diagrams, but not the keybindings, which can now be changed on the menu.
* AscendedGlitch:
** A certain Womb room would spawn two Larry Jrs and a Chub, but due to engine constraints the Chub would be without her third section and unable to spawn enemies. When the room was ported over to ''Rebirth'', this "buttless Chub" was left in faithfully.
** The Liberty Cap still retains its oddball ability to sometimes act as a compass instead of a mushroom item.
** You can still walk diagonally through spikes and not take damage if you get it pixel perfect. In addition, one possible Curse Room layout has a Red Chest guarded by four "Eternal" fireplaces, and you can walk through those to open the chest if you're careful enough, though you can also blow them up with bombs.
** Conquest could randomly replace War in the Depths 1 in the original game due to a glitch. Here, Conquest is both a Depths 1 and Womb 1 boss.
* AscendedMeme: The in-game description for the Cancer trinket is now "Yay, Cancer!", recognizing a meme that spawned from the people expressing happiness at receiving Cancer (a useful trinket) and [[ARareSentence other improbable phrases]] that only make sense in ''The Binding of Isaac''.
** Additionally, beating [[spoiler: Mega Satan]] as ??? unlocks a multiplayer baby called "[[FanNickname Blue Baby]]".
* BackFromTheDead: ''Rebirth'' continues the trend from ''Wrath of the Lamb'' of making undead versions of existing bosses, in this case applying it for nearly all normal bosses. Note that being undead usually makes each boss even ''more'' dangerous than before.
* BigHeadMode: Entering "[=T0PH EAVY=]" as your seed gives your character [[http://images.akamai.steamusercontent.com/ugc/517134452472044271/DB7F87C0DA17CB7C7AF101057F18130F358939A4/ a head that's at least 5 times bigger than their body.]] On the other hand, entering "[=T1NY D0ME=]" [[http://platinumgod.co.uk/images/seeds/T1NYD0ME.jpg gives you]] [[InvertedTrope Small Head Mode]].
* BigNo: One trinket is a crossed circle whose description reads "NO! Never again!" It removes space bar items from the item pool, which is good when you're collecting stuff to randomize with the D4.
* BlackMarket: In ''Rebirth'', finding a hidden passageway beneath rocks may sometimes lead to a modified shop which lets you pay hearts for shop items instead of coins. It also has a trap door to the next level, all three beggars, and sometimes a slot machine (type varies).
* BlackSpeech: The incomprehensible, guttural chanting in the Sheol theme could count.
* BondageIsBad: A new item in ''Rebirth'', "Gimpy'', is a black leather gimp mask. It's found in the Devil Room for the cost of one heart, or in regular Item Rooms.
* BonusBoss: ''Afterbirth'' plays with this in regards to [[spoiler:Hush]]. You do have to beat it at least once with every character, but unlike [[spoiler:Mega Satan]], this boss does not end the run. Rather, it is an optional diversion that can net you some extra items at the cost of fighting an extra boss, and once you beat it, you go right to [[spoiler:Sheol or the Cathedral]].
* BossOnlyLevel: [[spoiler:The Blue Womb contains two Item Rooms, a Shop, and a single 2x2 room with Hush in it.]]
* BossRush:
** Accessible by beating Mom in under 20 minutes. You have to fight through a total of 30 bosses in 15 pairs, but you're given a free item (out of four choices) to start and a second item if you win (whether they're helpful or not is another matter).
** [[spoiler:Mega Satan summons all the Horseman, all the Super Sins and the Angels during the battle.]]
* {{Bowdlerise}}: Inverted in the credits, which thank everyone who played the [[strike:heck]] hell out of the original.
* BraggingRightsReward:
** Prior to the ''Afterbirth'' expansion, there was no practical reason to beat [[spoiler:Mega Satan]] other than seeing the final ending. There were no unlocks for doing so, no achievements for doing so, not even a mark on that character's boss kill list. [[CosmeticAward All you would receive was a new picture for your save file]].
** With the exception of [[spoiler:the Lost, who has an item unlock for beating every main boss]], Hard mode has no item unlocks, and its associated achievements only require you to beat Mom's Heart/It Lives to unlock co-op babies. Beating the {{Brutal Bonus Level}}s is purely for sport.
** The unlock for beating the BonusBoss with [[spoiler:Keeper]]? Said character starts with a penny. Of course, you're earning that penny by killing what is arguably the hardest boss in the game with a borderline JokeCharacter.
* BulletHell:
** The battles against [[spoiler:Mom's Heart/It Lives, Isaac, ???, and Mega Satan]] offer (a mild example of) this.
** ''Afterbirth'' adds a true example of this, [[spoiler:Hush, an [[BonusBoss extra boss]] that spawns hundreds of enemies and normalizes the damage it takes, meaning even an overpowered build can't just cheese it.]]
** ''Afterbirth +'' has another fine example in the form of [[spoiler:Delirium, the new TrueFinalBoss. He combines complex bullet patterns with impredictable shapeshifting and erratic TeleportSpam. Add his ''massive'' hp and you have a pretty challenging boss in your hands]].
* CallBack: One of the new items in ''Afterbirth'' is actually an old item: [[http://bindingofisaacrebirth.gamepedia.com/Lusty_Blood Lusty Blood]] is just [[http://bindingofisaac.wikia.com/wiki/Bloody_Lust Bloody Lust as it worked in the original Isaac.]]
* CatScare: The final stage of Greed Mode is named [[spoiler: Ultra Greed]]. At the start of the stage, there's a boss room. You enter it, expecting a hard boss battle...[[spoiler: and then a single Monstro (or a pack of Greeds) appears. Ultra Greed is in the ''[[TrickBoss next]]'' [[YourPrincessIsInAnotherCastle boss room]].]]
* CastFromMoney: The Magic Fingers is an item that instantly deals a small amount of damage to every enemy in the room every time you put a penny into it. It has no cooldown time, so if you have lots of money (or are lucky enough to find the Dollar), you can spam it...until your money runs out, anyway.
* ChestMonster: ''Afterbirth+'' added a chest type that looks normal but becomes spiked when you stand right next to it. After some complaints, the chests were redesigned so that the difference between them and standard brown type was more obvious.
* ClassicCheatCode: Some seeds have interesting effects, such as BRWN SNKE ([[ToiletHumor causes Isaac to leave a trail of poop wherever he goes]]) or [=B00BT00B=], described below.
** Taken even further in ''Afterbirth'', where all those special seeds are now available in a list after you put one in, although the icon that indicates the list seems to indicate an EasterEgg, and can be chosen for any play, as well as removing the ability to progress in unlocks with some. They've all but been named cheatcodes. There is even one that makes Isaac invincible: [[spoiler: [=ALM1=] GHTY]]
* CoolHat: The Host Hat, an item introduced in "Afterbirth". It's a [[ExactlyWhatItSaysOnTheTin Host that Isaac wears on his head]]. It protects Isaac from explosions, and has a chance to block incoming shots and counter with the Hosts' signature three-bullet spread.
* ColorCodedForYourConvenience: Champion enemies have traits based on their suit of color, and all of them do one heart of damage rather than half. Dark green means an enemy [[MadeOfExplodium explodes]] at death and drops a bomb, pale red means [[DamageSpongeBoss massive HP]], dark red means regeneration with a double-heart drop, gray deals double damage and drops a key, light blue means it explodes into bullets on death, green leaves a trail of green creep and drops a pill, and dark blue generally means "less dangerous, but can still hurt you" and gives friendly flies.
* ContractualBossImmunity: [[spoiler:[[TrueFinalBoss Delerium]]]] is the only boss with a single phase that is immune to the Chaos Card. It isn't immune to [[TakingYouWithMe Plan C]], which destroys everything in a room and kills you three seconds later, but its death animation takes longer than three seconds. Only Lazarus or a character with Lazarus' Rags (both of which respawn the player in the same room) can make use of this strategy, limiting any unlocks to Lazarus alone.
* CombinatorialExplosion: Part of the update to the game is that this can now happen. The formula is no longer ''"pick up anything that can help you, hope for Mom's Knife or Brimstone"'' for a win that seems assured; now any number of items can assure victory in combination. Two wildly differing examples are Midas Touch + Book of Shadows + Nine-Volt, which basically gives you the ability to go running around turning enemies into coins every 2 rooms, and Ludovico Technique + magnetic tears + shielded tears, which give you a single controllable projectile that pulls in enemies and shots while disabling all shots that touch it meaning that you have control of basically a black hole against your enemies.
** Another mild game-breaker is homing shots plus Technology 1 or 2. The laser beam actually curves itself around to hit enemies.
** A further combo involves Guppy's Hairball and How To Jump. Jump over enemies to avoid them, and the hairball will plow through them. The momentum will also cause the hairball to bounce about well beyond its normal range.
** And pretty much anything plus Brimstone. Homing Brimstone? (if combined with Spoon Bender) Triple Brimstone? (if combined with Third Eye) ''Ten beams firing simultaneously in all directions''...''[[RuleOfThree Brimstone]]''? (if combined with Tammy's Head).
* CoOpMultiplayer: You can sacrifice one of your hearts to allow another player to create and control a familiar. Some of these familiars have special abilities, and some are unlocked by beating [[spoiler: Mom's Heart]] on Hard Mode.
* CounterAttack: Evil (black) hearts inflict the Necronomicon effect on all enemies in the room when a full black heart is depleted. In fact, ''Rebirth'' includes many items that damage enemies when Isaac takes damage. An example is The Negative, the new counterpart of The Polaroid.
* CursedWithAwesome: One of the random curses that you can get inflicted with is "Curse of the Labyrinth", which essentially merges two floors and forces you to fight two bosses in a row at the end. If you get it on the first floor, both treasure rooms will now be unlocked, sparing you the need for one key. On the other hand, later floors can potentially rob you of an additional Devil/Angel Room that could have spawned for both floors.
* DamageSpongeBoss: While there were already bosses who had this as their gimmick, this is taken to extremes as one of many gimmicks for the two new major bosses of ''Afterbirth'', [[spoiler:Hush and Ultra Greed]], who both have health that eclipses the health of every other boss in the game and even normalize the damage you deal to them, meaning that something that would one-shot every other boss in the game will only deal chip damage to them. ''Afterbirth +'' subverts this with [[spoiler:Ultra Greedier]], who has less health than [[spoiler:Ultra Greed]], yet plays this straight with [[spoiler:Delirium]], who doesn't need normalized damage because he has more HP than even [[spoiler:Hush]].
* DamnYouMuscleMemory: An odd variant--the game's new engine will trick some people up. ''Rebirth's'' new engine is extremely powerful, able to handle insane amounts of stuff on the screen at any time at a rock-solid 60fps even on lower-end video cards, but this has some unfortunate effects on people transitioning from the lower, glitchier framerate of the first. People who are accustomed to the half-second pause when transitioning into a room will routinely screw themselves over on hazards, and attacks are much harder to dodge thanks to a lack of HitboxDissonance.
** Most throwable items are used by pressing the appropriate key and aimed using the keys for firing tears. The Chaos Card, however, is automatically thrown in the direction Isaac's body is facing, meaning that it is aimed by walking in the direction you want to throw the card and ''then'' hitting the "use item" key. Woe betide the player who saves one far a particularly tough boss, forgets how to aim it, and ends up throwing it into the bottom wall.
* DarkerAndEdgier: Even though the regular game is fairly grim on its own, ''Rebirth'' has a much more oppressing and bleak atmosphere, compared to the cartoony and lighthearted (if drenched in BlackComedy) atmosphere of the first.
* DarkIsNotEvil: The Dark Bum, a demonic version of Bum Friend with a description of "He wants to take your life"... meaning he wants to take those red hearts that you can't take because your health is full and turn them into soul hearts (and the occasional spider. Being sick sucks). His usefulness (even after two nerfs) and fairly common appearance rate has pretty much made him an EnsembleDarkHorse, complete with [[https://twitter.com/darkbum Twitter page]].
* DeathDealer: Completely literally with the Chaos Card, which instantly kills ''anything'' it hits when thrown. It can even one-shot bosses! [[spoiler:Except [[TrueFinalBoss Delirium]]. [[NoSell It doesn't work on him.]]]]
* DevelopersForesight:
** The various insects you see--not the enemies you're supposed to kill but the actual pixel-tiny insects that add to the atmosphere--are interactive. Shoot or step on one and they'll turn into small puddles of blood. If you shoot a fly, tiny pixels of blood will fly off and they'll actually spiral downwards to the floor! If you have [[BulletDodgesYou the Soul]], bugs will be steered away from you.
** If you're at half a heart left and you enter a new room, [[PottyFailure Isaac will pee a little at the entrance]] showing how terrified he (and possibly you, the player) is at what dangers this new room may present that could end your run.
** In ''Afterbirth'', the Flush item (which normally [[ContractualBossImmunity has no effect on bosses]]) instantly kills [[TalkingPoo Dingle, Dangle, and Brownie]] when used.
** When you defeat Ultra Greed, he turns into a giant gold statue. Midas's Touch will instantly do this, obliterating his armor reduction.
** In ''Afterbirth +'', Glyph of Balance alters the drops of champion enemies so that you'll get what you need the most. If you're almost dead, its first priority is giving you a red heart - unless you have no heart containers, in which case it'll give you a soul heart instead.
* DifficultButAwesome:
** Anti-Gravity Tears can be very difficult to use, but when used well you can simply drag any enemy that chases you through a path of tears, set traps for enemies that love to jump on your head, and burst down enemies that only expose themselves to damage every so often. Goes UpToEleven with Brimstone: It can be difficult to make every laser hit, but you can now fire full-power Brimstone shots ''as fast as you can charge them''.
** Bob's Brain is notorious for blowing up in people's faces and generally being more trouble than it's worth. However, if you can keep track of its respawn time, keep repositioning so it doesn't immediately blow up in front of you, and LeadTheTarget so it hits what you want, it can function as a high-damage grenade launcher that continually replenishes itself. Particularly skilled users can even time it so that it blows up enemies when they're near bomb-able locations, saving on bombs in the long run. It shows up more frequently than a lot of items, giving players more incentive to learn how to use it properly.
* DownerEnding: The endings added by the expansions make it clear [[spoiler:Isaac thought himself to really be corrupt by sin and was driven to suicide]]. The 20th ending in ''Afterbirth+'' puts everything [[MindScrewdriver more or less into perspective]].
** [[spoiler:Isaac starves and suffocates to death inside the chest while hallucinating the entire game. His mother believes him to be missing and only finds out the truth when there are only bones left inside the chest. We then see Isaac walking into the underworld, followed by a demonic shadow.]]
** The Greed mode's ending features Isaac [[spoiler:getting trapped by a cave-in and becoming Greed after hanging himself. In the Greedier ending, his head then comes off and a fountain of bugs gush out of it. [[GainaxEnding How this fits with the other endings is anyone's guess]]]]...
* DunceCap: The Wiz powerup in ''Afterbirth'' is a dunce cap that gives the player character permanently crossed eyes (similarly to the "r u a wizard" pill).
* DyingDream: [[spoiler:''Afterbith+'' reveals that the whole game is this. Even his mother attempting to kill him was allegedly imagined]].
* EarlyGameHell: The hardest parts of Greed Mode are often the early levels, when you have little health and only average tears and damage. Once you've gained a few items, your chances of survival increase dramatically.
* EldritchAbomination: In ''Afterbirth'', collecting three Devil items transforms you into Leviathan (a mini-Cthulhu), which grants flight and a few extra black hearts.
* EnemyScan: The Spider Mod in ''Afterbirth'' gives every enemy (and segments if applicable) a visible health bar so you can track how much damage they've taken. It also displays how much damage your weapons are doing. Finally, the spider familiar itself wanders around randomly and can cause random effects to any enemy that touches it.
* EscortMission:
** Isaac's Heart makes Isaac immune to damage, but generates a heart familiar which takes damage in his place. Enemies will target the heart instead of Isaac, so it has to be protected. On the plus side, Isaac can use any self-damage item for free.
** The Guardian challenge gives you a character with invincibility, flight and a powerful sword to stab monsters with. The catch? You must protect a Punching Bag with Isaac's Heart attached to it. The Punching Bag takes damage, not the heart, and you have no control over how the Punching Bag behaves. You have to escort him all the way to Womb II. Most of the time, [[LuckBasedMission it is impossible]] to prevent the dude from getting hit a handful of times, though at least it tries to avoid traps in rooms. Usually. It's especially bad when you end up with charger-type bosses that can't be knocked off course, which means the Punching Bag is guaranteed to take hits.
* ExactWords: The Suicide King card's description is "A true ending." FromACertainPointOfView, it does just that, since [[spoiler: it drops several items then kills you.]]
* {{Feelies}}: The ''Nintendo Switch'' boxed release includes a fully illustrated instruction manual, which parodies the original ''Legend of Zelda'' game manual, as well as some stickers featuring some of the game's character's and enemies.
* FireWaterJuxtaposition: The new alternate chapters for the Basement and the Caves in ''Afterbirth'', Burning Basement and Flooded Caves.
* GameBreakingBug:
** There seems to be a game crashing bug that crashes the game when enough damage is done to [[spoiler: Mega Satan]] that they die without changing forms. It's rare, but it appears to be very consistent.
** Sad Bombs give bombs a Tammy's Head effect. [[spoiler:Godhead adds a giant halo to each tear.]] There's a glitch that allows one to let loose as many bombs as the screen will handle. Combining all three is the only way outside of [[spoiler:Mega Satan]] to crash the game.
** In ''Afterbirth'', Ending 17 is supposed to be unlocked by defeating [[spoiler:Hush]] at ???, but it only works once. On replays the player receives the exits to the next chapter instead. The problem back when the expansion was released is that imported saves from ''Rebirth'' wouldn't get the ending chest if they already had Chapter 5 unlocked. Trying to enter ??? as some characters would always crash the game, too.
** Alluded to by the ''Afterbirth'' item GB Bug, which has the description "Game breaking bug, right away!" It adds a "glitchy" familiar that bounces around the room inflicting random status effects on enemies.
** [[spoiler:Delirium]] is meant to be completely immune to the Chaos Card but when it gain multiple hitboxes it becomes vulnerable. Which isn't supposed to happen and the game crashes. Time to hope you brought good items.
* GameplayAndStoryIntegration: One of the new rooms is a bedroom where Isaac can sleep in a bed to recover health. In the center of the room, there is a rug. [[spoiler: Blow it up with a bomb to reveal a hatch to the next floor or a crawlspace. You may want to rewatch the intro at this point.]]
* GlassCannon: ''Afterbirth'' added a ''literal'' Glass Cannon, which grants a powerful, reusable shot but also reduces Issac's health to just half a heart. A patch nerfed it hard so it takes away all three kinds of hearts.
* GlassWeapon: In ''Afterbirth'' you can create the Glass Cannon, which is exactly what it sounds like, in [[GlassCannon every sense]]. It's incredibly powerful, but lowers your health to just 1/2 heart, meaning that you'll be killed in a single blow if something hits you.
* GuideDangIt:
** Unlocking [[spoiler:the Lost]] would be a tall order for any one player to accomplish using only the resources made available in game, so much so that the process was ultimately figured out by some people data mining and spoiling it; this unsurprisingly prompted an upset response from creators Edmund [=McMillen=] and Tyrone Rodriguez, who noted it was meant to prompt an [[AlternateRealityGame ARG]]-type response with the community working and speculating to solve it. The process was meant to be a community effort, which probably would have worked eventually, but it is still fairly obscure. You either need to spend a long time going in circles and following vague clues to figure this out, though it should be noted that knowing what to do isn't [[SelfImposedChallenge half]] [[MoonLogicPuzzle of]] [[NintendoHard it.]] [[note]]To put it in perspective, the process involves dying in a certain room holding a certain item in order to receive one part of four images that hint at the actual unlock process, which involves dying with four certain characters in certain locations under certain circumstances in a certain order. ''Consecutively''.[[/note]] The unlock method has been significantly shortened (but made more luck-based) in ''Afterbirth'': [[spoiler: Die with any character in a Sacrifice Room, while holding the Missing Poster. The difficulty is now getting both items to appear in a run, since seeded runs do not work.]] However once you unlock them, you can use them in any run afterwards.
** Two stats are not shown on the stats screen, or elaborated upon at all. You have "Evil / Faith", which is a sliding scale determining what kind of special deal (Deal With The Devil or Deal With The Angel) you get when you qualify for one, and Shot Height, which is used as an alternative to range in some items that claim to increase it (notably increasing Shot Height as Azazel is a ''bad thing'' and makes his range ''shorter'').
** Different damage upgrades are "worth more" than others. Furthermore, some simply add to your damage stat (Damage +1 for instance), while others give you a multiplier instead, or on top of, adding to it, which is significantly better most of the time. The highest of both types are provided by, respectively, Ipecac (+40 damage) and Tough Love (3.2 damage multiplier for each tooth.)
** Special items are back! Not only was this completely unexpected due to Edmund outright saying they would be removed, they now work differently. Instead of the huge list of Special items from the original, there are now only fifteen: [[spoiler:Polyphemus, Mutant Spider, Brimstone, Sacred Heart, Soy Milk (no longer Special in ''Afterbirth''), Pyromaniac, Lil Brimstone, Ludovico Technique, Dr. Fetus, Epic Fetus, the D6, Mom's Knife, Stop Watch, the D100, and Godhead]]. What's more, the Special counter is changed based on sight, not pickup, meaning seeing some of the bad Special items will make it less likely you'll get good ones.
** Lazarus' entire playstyle is bizarre. He starts with a negative Luck stat (-1), and greatly benefits from ''dying'' as early on in the run as possible, since the item he starts with (Lazarus' Rags) give him a damage bonus when he revives.
** Unlocking the Blinding Baby requires you to use The Sun card via the Blank Card activated item. Either you get this one by accident or never figure it out on your own.
* HitboxDissonance:
** The wall-crawling spider type enemies have a damage hitbox that's extremely confusing, placed at least an inch away from the front of the actual model. Since this hasn't been fixed and the crawlers are often protected by a pit, this could be intentional to keep the game from becoming unwinnable by having extremely low range. Still, this can be frustrating when Brimstone and diagonal shots like tiny planet don't hurt them despite visibly touching them.
** This can happen to Isaac himself through size-altering pills. "One Makes You Larger" does ''not'' increase the size of Isaac's hitbox, but it does increase his visual size. "One Makes You Small" ''does'' decrease Isaac's hitbox along with his size.
* InstantRunes: The Black Powder in ''Afterbirth'' causes a trail of black powder to appear where you walk, which dissipates after a certain distance. Forming a circle with the powder forms a glowing red pentagram which damages any enemy that touches it.
* InterestingSituationDuel: The "Challenges" give you certain combinations of items that can drastically alter the way you play. For example, the "When Life Gives You Lemons" challenge mentioned below gives you Lemon Mishap (a JokeItem) and lowers your stats, but also gives you the Nun's Habit, Nine-Volt and a single Lemon Party pill. Since your stats are so bad, you'll have to rely on leading enemies into the damaging puddle dropped by Lemon Mishap until you get better items (but due to the Habit and Nine-Volt, you can use the Lemon Mishap in almost every room, more often if you take damage).
* InterfaceScrew: This game adds three new interfaces curses on top of Curse of the Lost (minimap disabled). Curse of the Unknown removes your health bar, forcing you to keep a mental tally. Curse of Darkness reduces the ambient lightning to almost nothing, though the player and most enemies glow. Curse of the Blind turns every pedestal item (activated and passive items) on the floor into a question mark, including Devil/Angel Room items and shop inventory. It'll make you think twice about picking something up.
* JackOfAllStats: Invoked by the Libra item, which actively balances your stats once you collect it. Can turn the player into a MasterOfNone or MasterOfAll, depending on what items it is mixed with.
* JumpScare: [[spoiler:Ending 3 a.k.a. The Rubber Cement ending.]]
* KaizoTrap:
** Mom's Heart now explodes into a radial bullet burst when killed. It's easy enough to dodge if you know it's coming, but a surprise nonetheless.
** Devil Rooms in ''Afterbirth'' have a chance to contain enemies that you have to kill in order to leave.
* LastLousyPoint:
** ''Rebirth'' is much worse about this than the original, especially with Secret Room items. Since the Secret Room is less likely to spawn items combined with more possible variations, most players resort to exploiting the item pool mechanics to reroll Secret Room items from Beggar drops or mushroom spawns. Another annoying item is Steven, which is now impossible to find except by killing Steven in a main boss fight (already rare to begin with), and only has a 1 in 5 chance of spawning compared to Little Steven. Rerolling also doesn't work on Steven drops, so it has to drop normally.
** Applies much less in Afterbirth: Greed Mode's restocking shops mechanic and expanded shop item pool means it is possible to see the secret room items there. As for Steven, it now drops in Golden Chests.
* LethalJokeWeapon: Because of the improved item synergies, many mediocre items can become the keystone to a weird yet highly effective setup. Bonus points if several if your items are bad but [[AllYourPowersCombined they become effective in tandem with each other.]]
** Lemon Mishap and Pinking Shears, two mediocre-at-best items in ''Wrath of the Lamb'', have been buffed to the point that they can singlehandedly kill bosses.
** "A Card Against Humanity". You'd be surprised at how badly some bosses handle a room full of poop. Becomes even better if you can remotely attack through Ludovico Technique, ???'s Only Friend, or Robo-Baby 2.0.
* LongSongShortScene: The [[spoiler:Blue Womb[=/=]???]] area gets a dang nice song, even though it is simply a single room before a boss fight.
* LuckBasedMission:
** Eden is entirely built around this trope, starting with random stats and items. However, using them requires "tokens", which are acquired by defeating Mom. This is to prevent SaveScumming for a set of good items, though it's easy enough to earn a large surplus if you use other characters consistently.
** "Dice Rooms" are rare rooms with [[ShapedLikeItself a giant die on the floor]]. Stepping on it may re-roll Isaac's items, reroll the pedestal items on the current floor, reroll the pickup items on the current floor, ''restart'' the current floor, or ''several of the above at once''. Using such a room can be the ultimate gamble.
* TheLoad: Familiars have the potential to screw you over to an even greater degree than before, especially when "free-roaming" and "explosives" are dangerously mixed. Special mention goes to the BBF (essentially a friendly Boom Fly) which combines ''both'' and is liable to blow up in your face if the enemy it collides with happens to be near you.
* LuckilyMyShieldWillProtectMe: The Trinity Shield blocks all bullet attacks from Isaac's front, moving with Isaac.
* MagikarpPower:
** One of the new ideas added to the game is the possibility of crippling yourself by picking up a bad item early, Tiny Planet and Bob's Brain to name two, in the hopes that later in the run you'll pick up an item that goes complements them really well, a high attack speed or piercing shots for tiny planet making it better than the pretty inaccurate item it is normally. One could argue it's part of what makes the game more fun than before, just the pure number of items that you might pick up and hold on to in the hopes they work exponentially well with another item you find on the run.
** The Void item added in ''Afterbirth+'' has two properties. This first, which is moderately useful, allows it to destroy any passive items in a room and covert them into random stat boosts, with a chance for a slight range reduction. The second, which applies to this trope, allows it to destroy any spacebar items and permanently copy their effects. There is no limit to how many items can be absorbed this way, and all of them will trigger each time Void is used. This can include generating Soul Hearts, Black Hearts, Eternal Hearts, mapping a floor, using Blank Card and its combos, Placebo and its combos (most importantly, '''infinite charge'''), four-way Brimstone from Krampus, and so forth. The only things it can't copy are spacebar items that are consumed upon use.
** Also in ''Afterbirth+'', the Smelter item. It takes 6 rooms to charge, and each use removes Trinket(s) and permanently applies its effect to Isaac. If you happen to find Mom's Box or a Fortune Teller machine, you'll quickly become unstoppable.
* MarathonLevel: The new VeryDefinitelyFinalDungeon, [[spoiler:the Void]], is this. It's as large as two XL Womb floors put together and has 6 or 7 boss rooms besides the FinalBoss fight, one of which always contains another "final" boss. Good luck finding your way there if you get hit by Curse of the Lost.
* MurderSuicide: [[InvokedTrope Invoked]] by a new item in ''Afterbirth +'', the Plan C. It instantly kills ''anything'' in the room (even final bosses)... and kills you shortly afterwards.
* MusicIsEighthNotes: The Dingle boss whistles to summon mooks. The audio is accompanied visually by a few eighth notes.
[[/folder]]

[[folder:N-Z]]
* {{Nerf}}: An inevitable result of re-balancing the game from ''Wrath of the Lamb'', several items and one character (Cain) were weakened for balancing purposes. On the flipside, Samson received a much-needed buff.
** The Bloody Lust mechanic change to powering from Samson taking hits instead of getting kills is a significant change of strategy for the worse due to his starting health.
** An ''Afterbirth'' patch nerfed Lilith's Box of Friends and Azazel's Mini Brimstone laser's power and charge time. Another patch un-nerfed Azazel's damage, but made his charge time ''worse''.
** ''Afterbirth'' also nerfed Judas's Book of Belial to only increase the chance of getting a Devil/Angel Room when held instead of guaranteeing one whenever possible.
** A patch for ''Afterbirth'' made a very controversial nerf to the [[PurposefullyOverpowered Stopwatch]]. Instead of having it slow down every enemy permanently, it was changed to activate only after taking damage ''and'' having its effect only last for one room. Many people were visibly upset by this, and in a later patch, while it kept its flaws, it was changed to [[ObviousRulePatch also activate if Holy Mantle's shield was broken]], which at least still makes it a very useful item when playing as [[spoiler:The Lost]].
* NewGamePlus: In ''Afterbirth +'', if you defeat the Lamb as your FinalBoss, you're given the option to do a "Victory Lap". You start from the first level with all your items intact. This can be done endlessly, and the game tracks how many times you repeat. Most achievements won't work in this mode (only the "U Broke It!" achievement can be earned on a Victory Lap). Further, on the third victory lap, the game increases in difficulty (you are turned into [[spoiler:the Lost]], minus his Holy Mantle and D4, and shops no longer appear).
* NiceHat: ''Afterbirth'' introduces the item Host Hat, which puts a Host on Isaac's head. The item's in-game description is even "Nice hat!"
* NintendoHard: A "hard" difficulty level has been added, which significantly dials up the amount of enemies and [[EliteMook champions]] while giving you less powerful items. ''Afterbirth+'' does this for Greed Mode, which is called Greedier Mode.
* NoFairCheating: Level seeds allow you to repeat a powerful run, but block any achievements. Similarly, challenge maps only allow you to unlock the associated achievement. Finally, the NewGamePlus blocks any achievements.
* NotTheIntendedUse:
** The [[spoiler:key pieces from the Angels]] are supposed to be used to unlock the TrueFinalBoss. However, if the player's objective is the regular boss of that floor, then these items can be rerolled with the D6, allowing for an extra Angel Room item. Players can also bet on getting Dad's Key later to sidestep the problem, but this is less likely.
** Also, Dead Cat (which gives you nine lives...at the cost of only having a single heart container for each life) can be used to purchase every Devil Room item for basically free: you pay for the Devil Room item with your last heart, you die, you get resurrected, you go back into the Devil Room, pick up the other Devil Room item, die again, get resurrected again, continue to the next floor with 7 lives remaining and two free items! If you're good at dodging, you probably don't need all nine lives anyway.
* OneHitKill: The Chaos Card kills almost anything in one hit. The only things that can survive it are [[spoiler:the first form of Satan, the first form of Mega Satan, Delirium ([[ContractualBossImmunity which is the only intentional exception]])]], and, likely due to a bug, Scolex.
** Plan C takes it a step further by [[SmartBomb instantly killing everything in the room]]. [[spoiler:Including Isaac.]]
* PajamaCladHero: The PJs ''"make you feel cozy"'', which shows by healing Isaac to full health and giving him four extra soul hearts on top of that.
* PowerUpLetdown:
** The general opinion of Bob's Brain. It's a minion/follower that charges into enemies in a straight line when "fired" along with Isaac's tears, exploding on contact. It will do this even if the enemy is right next to Isaac, causing him to take SplashDamage. It also doesn't explode on the return trip if it misses, making it hard to aim, and doesn't synchronize well with tears. BBF (Big Beautiful Fly) also falls into this category for exploding upon contact with enemies (regardless of location) though at least BBF's movement is predictable and can be accounted for.
** Thought that Samson or [[spoiler:???]] wasn't worth the effort in the original? The crappy reward-to-effort ratio for [[spoiler: The Lost]], a genuine JokeCharacter, is even ''worse''.
** The Suicide King special tarot card requires beating one of the more infuriating challenges to unlock and has the splendid effect of dropping 10 items... and killing you.
** The Lord of the Flies transformation gives you flight, and makes all enemy flies into friendly blue flies. That's about it... At least it's free flight, but Guppy is far superior.
** The new transformations in ''Afterbirth'' range from helpful to nearly pointless. The Mushroom, for example, is just a free Health Up.
** Tiny Planet, which makes your shots orbit you at a fixed distance instead of going forward... which makes it almost impossible to hit anything with more than half your shots, forces you to fight at close range, and makes knockback useless for defense. At least it works differently with a few alternate attacks (notably Brimstone).
** Curse of the Tower, unless you have an item that provides bomb immunity or invincibility after being hit. It spawns a handful of troll bombs any time you take damage, dealing lots of damage to anything in the room--but possibly also damaging you again. And it will destroy any blood donation machines or demon beggars you try to use.
** If you manage to defeat one of the hardest bosses in the game with the Keeper, one of the hardest characters in the game, you are rewarded with... him starting with a single penny in future runs. Gee, thanks.
** The Wiz allows Isaac to shoot tears out of both eyes at once, but also forces him to shoot diagonally (effectively a permanent "R U A Wizard" effect). Given that the game is designed around shooting in the cardinal directions, it's generally more of a hassle than a benefit.
* PromotedToPlayable: Some of the hidden items from the original game are now unlocked from the start in ''Rebirth''. Other items now have different unlock requirements, such as The Nail. And inverted with a few items that didn't need to be unlocked in vanilla, such as the Wire Coat Hanger.
* PurposelyOverpowered:
** The Stopwatch. Unlocking it requires you to put 999 coins in the Donation Machine (which can take dozens of runs since the Donation Machine will randomly jam and refuse further donations for that run). Once you have it, it slows down all enemies and their bullets for the duration of that run, making it a near-cakewalk. It got hit with a huge nerf in ''Afterbirth'' via a patch, reducing it to an on-hit, single room effect (still pretty good against bosses, but not quite as useful overall).
** The Mega Blast is Brimstone or Krampus' Head on crack. It gives you Mega Satan's giant Brimstone laser, which lasts a solid 15 seconds and persists between rooms, allowing you to steamroll through numerous rooms before the laser runs out. However, this requires beating [[spoiler:[[HarderThanHard Mega Satan]]]] with every character, including the JokeCharacter AND it's the only item in the game with a 12-room charge (and batteries only refill 25% of the charge bar), so you'll only be able to use it once every two floors, or once a floor if you're lucky. With the addition of Void in ''Afterbirth +'', you can even bypass the long charge time.
** Mama Mega! is this. When used, it deals kills every normal enemy in a room (if an enemy spawns another upon death, you have to kill them yourself), does massive damage to bosses, destroys all forms of rocks (but not Keepers or rocky chests), opens all Secret and Super Secret Rooms, and even opens the paths to Boss Rush and the Blue Womb if you've passed the time limit for either. Best of all, it lasts for the entire floor on which it is used. It basically gives you an entire "free" floor with nothing standing in your way.
* RecurringBoss:
** Depending on your choices and luck, you may fight The Fallen as a boss four times in a single run: once at a random level, once during the boss rush, once as a Double boss in the Womb, and once guarding Satan. Not counting the times it shows up as a regular room enemy and its slight recoloring Krampus.
** Similarly, the Greed/Super Greed battle is almost guaranteed to replace one of the shop rooms or secret rooms you've striven to unlock. Bonus points if the two show up on consecutive floors. He's so common, that a trinket, [[spoiler:Greed's Rib]], added in ''Afterbirth'', prevents any form of Greed from appearing.
** There are four completely different Gurdy bosses for various stages in her life cycle, which can be fought in each of the four main areas of the game. You can potentially fight them all in one run.
** In Greed mode, you are naturally quite likely to fight several copies of Greed and/or Super Greed on the penultimate level, then fight several more copies at the beginning of the final level. And then you fight Ultra Greed.
* {{Retraux}}: ''Rebirth'''s art style is intended to resemble a colorized Gameboy game. Additionally, there is an arcade filter available by using the [=B00BT00B=] seed code. ''Afterbirth'' adds a Retro Vision pill which pixelates the screen on and off for a minute or so.
* RockMeAsmodeus: ''Hericide'', [[spoiler:Satan]]'s new boss theme.
* SaveScumming: Intentionally discouraged with the increased item synergies in the hopes that players stop immediately restarting when they get a bad item early on. Then again, the seeding tools provide for a form of this if one gets particularly lucky with their game's generation and want to retry after dying partway through.
** Also discouraged with Eden. Eden starts with random stats and items, so selecting Eden requires and consumes an Eden Token gained by beating end-game bosses. But if you're a good enough Isaac player you'll have more Eden Tokens than you know what to do with.
** By forcing the game to quit before the Game Over screen comes up you can reload your last suspend save, but never collect Guppy's Collar while doing this. The game forces 1-up effects when you save scum and the Collar works by either reviving or killing you.
** ''Afterbirth +'' punishes repeated resets with the Mr. Resetti achievement: it unlocks [[PowerUpLetDown half soul hearts]] for the next runs.
* SchmuckBait: There's an unlockable tarot card called [[spoiler:Suicide King.]] Upside, it spawns a bunch of cool pickups. Downside? [[spoiler:[[ExactlyWhatItSaysOnTheTin You die]]]].
* SecretCharacter: A new one for this version. [[spoiler:"The Lost", a OneHitPointWonder incapable of gaining [[OneHitPointWonder any hearts]] and starts with flight.]] Unlocking him is a real GuideDangIt: the old way was to [[spoiler:die to Mullibooms as Isaac on the basement, then to your own bombs as Maggie in the caves, then to Mom as Judas, then to Satan stage 2 as Azazel, with no deaths in-between and in that order.]] In ''Afterbirth'', you just have to [[spoiler:kill yourself in the Sacrifice Room with the Missing Poster in your inventory]].
** Another one was added in ''Afterbirth'': [[spoiler:The Keeper. He uses coins for health and converts all hearts into blue flies. He can only have up to 2 coins worth of health at a time, yet while he can't gain any, he can still ''lose'' them. On top of that, he's slow and fires triple shots at reduced speed.]]
* SequelDifficultySpike:
** Zig-Zagged. ''Rebirth'' adds a lot of new content while updating older items from the original, which makes things both more difficult and easier thanks to the new items but larger item pool. The shop gets a major revamp with a lot of very useful items to potentially buy. The main bosses are a straight example, all of them having been given new moves and BulletHell abilities which make the fights twice as hard as they were in the original game.
** The ''Afterbirth'' expansion adds new features to the level design such as cramped rooms and trap rooms. Multiple bosses at cramped rooms don't mix well. And certain trap rooms only give you a split second to react before a bomb explodes in your face. There are also trapped treasure rooms which might require you to use a bomb to reach the item.
* SillinessSwitch: Some special seeds you can type in have strange and sometimes hilarious effects. For example, FART SNDS turns all sound effects in the game into, you guessed it, fart sounds. Find a nickel? ''Pffrt''. Open a door? ''Ffrrp''. Take damage? ''Prpfff''. Another good one is SLOW 4ME2, which increases or decreases the background music tempo depending on how fast you're moving.
** As of ''Afterbirth'', inputting a special seed permanently unlocks its effect, and ''any number'' can be toggled in a new [[EasterEgg menu of Easter Eggs.]][[labelnote:Spoiler]]Press Q (or LB) on the character select screen.[[/labelnote]]
* SolidGoldPoop: In ''Rebirth'', any run-of-the-mill poop piles you find have a chance to be golden poop piles, which drop a bunch of coins or the Counterfit Coin trinket when destroyed. [[spoiler:Having The Poop active item and Midas' Touch will let you spawn these every single room.]]
* SpeedRun:
** Now actively encouraged, since many features were added to help out the dedicated SpeedRun community. All runs have an internal timer attached to them (viewable by pulling up the map, which also displays the current level for screenshot purposes) and the game keeps track of your best times for fresh runs as each character (i.e. randomly generated, not from a seed). The main purpose of seeds was to allow for many people to play the same run and compare completion times, since without seeds the times were too often influenced by the RandomNumberGod. There are now leaderboards for the quickest runs for a particular daily seed and [[SeriousBusiness competitive speed-running]] may very well arise.
** Additionally, beating Mom in under 20 minutes grants access to the special BossRush room. The little clock that's visible during each loading screen shows how much time is left until this room expires, and you can bring up the map to check your current time.
** The Speed! challenge requires you to beat It Lives in 16 minutes, or every 10 seconds you take a half-heart of damage. On top of that, all enemies and their bullets move twice as fast.
** In ''Afterbirth'', defeating Mom's Heart/It Lives in under 30 minutes grants access to [[spoiler:The Blue Womb and the BonusBoss Hush]].
** In ''Afterbirth+'', one achievement (and a new item) can only be unlocked by beating the Lamb in under 20 minutes. [[ThatOneAchievement Good luck with that.]]
* SpreadShot: Where to start? Several enemies use these, and there are ''many'' items that allow the player to fire in spreads.
* StandardStatusEffects: The Iron Bar item adds a Concussion tear effect, which confuses enemies. The Charm tear effect causes enemies to actively seek out and damage other enemies, if they are capable of doing so (enemies stuck on a certain path, such as rolling guts, don't seek out other enemies); the charmed enemy can still damage you, however. The Fear tear effect causes enemies to slowly run away from you, and stops some enemies from firing at you. The Fire tear effect deals some brief continuous damage after hitting an enemy, and causes occasional fiery explosions. The Slow and Poison effects return from the original game. They're unchanged except affected enemies now have an icon above their heads.
* StealthPun: The Latchkey gives you [[LockAndKeyPuzzle Luck and Keys]].
* {{Stonewall}}: One of the new items, Punching Bag, gives you a friendly Mulligan that acts as a tank for you.
* StuckItems: You're still stuck with whatever is held in your use slot like in the first game until you find another usable item. However, it's thankfully averted with pills, trinkets and tarot cards, which can be dropped by holding down the map button (or the left Ctrl button on your keyboard). But even the map button cannot get rid of the Tick trinket, which is the one truly irremovable item in the game.
* SuperPrototype: Technology 0.5 is a far superior laser when compared to Technology and Technology 2. It doesn't replace your regular tears so is a direct firepower upgrade when you pick it up, doesn't have a damage multiplier reduction built into its stats and perfectly synergizes with your power-ups. It also randomly adds power-up effects. Its only downside is that it occasionally misfires, but you'll barely even notice it.
* SuspiciousVideoGameGenerosity: The item pool got buffed ''again'' from ''Wrath of the Lamb'' by introducing items that confer benefits worth two separate items from "Vanilla" ''Isaac''. You'll need those buffs for sure...
* TalkingPoo: The Dingle boss, and his minions (Squirts).
** ''Afterbirth'' adds [[PaletteSwap Dangle]] and Brownie.
* ThemeNaming: The {{Disc One Final Boss}}es [[spoiler:and ''Rebirth''[='=]s True Final Boss]] all have boss themes that end in ''cide''. (''Matricide'', [[spoiler:''Ventricide'', ''Hericide'', and ''Infanticide''.]] Averted with the [[spoiler:fake]] {{True Final Boss}}es, who have uniquely named themes ([[spoiler:''Ascension'' and ''The Fallen Angel'']])
* ThiefBag: In ''Afterbirth'', money bags will occasionally spawn that drop a few bombs, coins, or keys when grabbed.
* TooAwesomeToUse:
** The Friendly Ball allows you to "capture" an enemy and release it to fight with you until it dies, persisting between rooms and floors. However, since the item has a 4-room recharge, it can take at least eight rooms in order to successfully release an enemy you captured, and even then your new companion will most likely die after a couple rooms.
** Mega Blast is an activated item which fires a massive Brimstone laser which does insane damage and persists between rooms and floors, lasting for fifteen seconds. However, not only does it have a 12-room recharge (the only item in the game to require that many rooms), but the battery pickup will not fully recharge the item for another go. Because of this, Mega Blast tends to be saved for endgame floors/bosses that players want to wipe out quickly, such as the [[DamageSpongeBoss insanely tanky]] BonusBoss.
** The Chaos Card can OneHitKill ''literally anything'' in the game. The catch, of course, is that it's a card and can therefore only be used once. Like Mega Blast above, the Chaos Card tends to be saved for endgame bosses such as said insanely tanky BonusBoss. Unless, of course, the player gets a Blank Card...
** Diplopia is an activated item that doubles every pickup and collectible item in the room. With the number of items in the game that stack with themselves, this can create some insane synergies. However, it's only good once, and you can't cheat by using the ? Card to duplicate its effect because doing so consumes Diplopia anyway for no additional benefit. It often comes down to a decision regarding whether to use it on the decent item you have in front of you, or to hold onto it in hopes of getting a better item to duplicate later on.
* TookALevelInBadass: A number of characters, playable and otherwise:
** Mom's Heart/It Lives was a rather straightforward FlunkyBoss in the original game. This time around... let's just say that BulletHell veterans will feel right at home.
** [[spoiler:Isaac/???]] likewise get a bullet hell buff and new attacks.
*** Isaac's third form is [[InvertedTrope considerably easier]] in Rebirth - his light attacks are easy enough to avoid as you can guess the pattern of the safe zones, plus his bullet hell attack has a much shorter range, is easier to dodge and is not homing. And he doesn't spawn angels in this phase.
** Eve has more health and Whore of Babylon kicks in at one full heart instead of a half, allowing her to take advantage of the serious damage buff while still being able to endure a blow from most early game enemies, giving her a chance to build up a buffer of spirit hearts.
** Samson has much more health, increases damage done for every hit he takes, has much larger range, and keeps accrued bonuses across the entire ''floor'' instead of just the room.
** Most characters receive an upgrade to their starting load out once certain conditions are met. Such as Cain starting with the Paper Clip (unlocks Gold Chest for free) or Eve starting with the Razor Blade (boost damage for the room at the cost of a heart, letter her trigger Whore of Babylon at will).
* TrueFinalBoss: Attempts always end after a certain boss, though unlocking more stuff and meeting certain requirements can result in the bar being raised on who is considered the final boss; for example, the very first run ends with Mom at stage six, though beating her a second time spawns the door to the next stage, where players have to fight the new final boss, [[spoiler:Mom's Heart]]. Assuming everything is done perfectly, you have to reach the credits ''eighteen'' times to unlock TheVeryDefinitelyFinalDungeon and face the [[spoiler:8]]th final boss.[[labelnote:exp.(spoilers!)]]First run ends at Mom, unlocks Womb; eleven runs to unlock It Lives! and Cathedral/Sheol access; five runs to kill Isaac/Satan to unlock The Chest/The Darkroom access; one run to kill either ???/The Lamb and spawn the Golden Gate.[[/labelnote]]
** However, with a bit of SequenceBreaking using [[spoiler:a Devil Room that spawns after the Mom's Heart fight, which always leads to Sheol even if you haven't yet unlocked It Lives!]], one can theoretically reduce this to eight runs[[labelnote:exp.(spoilers!)]]1 run to unlock the Womb, 1 run with the Devil Room to defeat Satan (and unlock Judas, whose starting item guarantees a Devil Room will spawn whenever possible), 5 more runs to unlock the Negative, 1 run to defeat the Lamb and unlock the Golden Door.[[/labelnote]]. Still quite a few runs though.
** In ''Afterbirth '' there is the True ''True'' Final Boss in the [[TheVeryDefinitelyFinalDungeon Truly Final Dungeon]], [[spoiler: Delirium]].
* UnexpectedGameplayChange: Some challenges take away your tears completely and force you to fight with either attack familiars or a recharging spacebar item and maxed bombs.
* UniqueEnemy:
** There's a blue-skinned variation of the Conjoined Fatty monster that has a very slight chance of appearing in the I AM ERROR room and [[spoiler:the Chest]]. Despite what its appearance may imply, it's completely distinct from a champion variant and attacks with vicious homing Ipecac shots.
** The bosses [[spoiler:Hush]] and [[spoiler:Ultra Greed]] spawn Gapers that are reskinned to fit the respective boss's motif. [[spoiler:Hush]] also spawns uniquely-skinned Ring Flies that form more complex formations than the normal variety and reskinned Boils with a different attack pattern.
** Two Stone Grimace varieties are extremely rare and only appear in one floor. One is the Broken Gaping Maw, which alternates between trying to suck the player character in with more force than the normal Gaping Maws and not doing anything, found only in [[spoiler:the Womb]] and neither of its alternate floors. The other is the Brimstone Grimace, which fires brimstone lasers and can only be found in [[spoiler:Sheol]]. It is possible to play the game for a long time through several runs without even seeing either of them.
* UnwinnableByMistake: The Blue Bomber challenge turns off your tears but gives you the Kamikaze spacebar item and Pyromaniac (immunity to bombs). Some enemies, however, are immune to Kamikaze, so you need bombs or another source of damage to kill them. If you have neither, you have to reset. Mercifully, a patch added [[CherryTapping Brother Bobby]] to the player's arsenal, which prevents the situation from being ''completely'' unwinnable.
* UpToEleven: ''Afterbirth'' has the XXXXXXXXL challenge, which is the "XL" level effect on steroids. All levels have a size which is roughly equal to an XL Womb level.
* VariableMix: If the room has a lot of enemies or there's a miniboss, an electric guitar harmony fades into the music.
* ViolationOfCommonSense: With a hard cap of 12 hearts compared to the original having no cap at all, it's actually to your benefit to only have a few red hearts. Having full health means you will be unable to pick up spirit hearts or the new black hearts (which deal full room damage when depleted, similar to the Death tarot card). This means runs in which a low number of health containers are found may actually be more viable. It also seems that spirit hearts are a bit more common, and black hearts are more likely to pop up than you might expect for something so useful.
* WesternZodiac: The 12 signs of the zodiac appear as upgrades for Isaac.
** Aries increases speed and lets you deal damage to enemies by running at them.
** Taurus slows the player down, but when in a room full of enemies you build up speed over time, eventually getting the My Little Unicorn effect.
** Gemini gives Isaac a little buddy attached to him that attacks enemies when they get close.
** Cancer gives 3 soul hearts and makes all damage reduced to 1/2 a heart when he takes damage in a room.
** Leo allows the player to break rocks, mushrooms, skulls, etc. by stepping on them.
** Virgo has a chance to make the player invincible after taking damage and makes all negative pills positive.
** Libra balances the player's stats and gives 6 coins, bombs, and keys.
** Scorpio gives the player's tears poison effects.
** Sagittarius makes the player's tears penetrate enemies and increases speed.
** Capricorn increases all stats.
** Aquarius leaves a trail of tears behind the player, damaging enemies that step in it.
** Pisces increases tear fire rate and the amount of knockback enemies take from tears.
** Finally, the Zodiac item takes the effect of a random zodiac sign every floor.
* WhamEpisode:
** The 15th and 16th ending. [[spoiler: Respectively, Isaac is shown to have gone missing, with his mom searching for him, and Isaac turns into a demon!]]
** Ending 17 and 18. [[spoiler:The first confirms Isaac died trapped inside the chest. The latter is another take on his death: he's crushed by debris while trapped on some cave and his corpse becomes Greed.]]
** Ending 20. [[spoiler:His mother trying to kill him was imagined. Isaac killed himself by locking himself up in the chest because he blamed himself for his family falling apart, thinking that he was corrupted by sin]].
* WingedSoulFliesOffAtDeath: The new death animation. [[spoiler: And it's a top secret character, called "The Lost"!]]
* AWinnerIsYou: Inserting coins into the Greed Donation Machine grants you a few unlocks for the first hundred or so. Originally, it stopped at around 109, but a patch allowed the player to set the donations towards 999, which does nothing but praise the player with fireworks at the end and award an achievement. [[spoiler:But something major happens if you donate one more coin...]]
* WhenLifeGivesYouLemons: The name of Challenge #12.
* WorldOfSymbolism: ''Isaac'' explores the same themes as most of Edmund [=McMillen=]'s older games, such as ''VideoGame/TimeFcuk'', but uses very different imagery to do so.
* WrapAround: The Continuum item grants this effect to your tears, causing them to pass through walls and emerge from the opposite side.
[[/folder]]
----
-> [[TheStinger Dear Diary]],
-> [[TvTropesWillRuinYourLife Today I died]]. I was killed by this page on [[Wiki/TVTropes some wiki]]. (ugly)
-> I leave all that I own to my pet cat Guppy. (Pretty cool stuff!)
-> Goodbye cruel world,
-> -XOXO Troper
----
qu
29th Jun '17 10:26:55 PM FlakyPorcupine
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--> ''"Isaac and his mother lived alone in a small house on a hill..."''
11th Jun '17 8:45:49 PM DastardlyDemolition
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** [[spoiler:Delirium]] is meant to be completely immune to the Chaos Card but when it gain multiple hitboxes it becomes vulnerable. Which isn't supposed to happen and the game crashes. Time to hope you brought good items.



** Unlocking [[spoiler:the Lost]] would be a tall order for any one player to accomplish using only the resources made available in game, so much so that the process was ultimately figured out by some people data mining and spoiling it; this unsurprisingly prompted an upset response from creators Edmund [=McMillen=] and Tyrone Rodriguez, who noted it was meant to prompt an [[AlternateRealityGame ARG]]-type response with the community working and speculating to solve it. The process was meant to be a community effort, which probably would have worked eventually, but it is still fairly obscure. You either need to spend a long time going in circles and following vague clues to figure this out, though it should be noted that knowing what to do isn't [[SelfImposedChallenge half]] [[MoonLogicPuzzle of]] [[NintendoHard it.]] [[note]]To put it in perspective, the process involves dying in a certain room holding a certain item in order to receive one part of four images that hint at the actual unlock process, which involves dying with four certain characters in certain locations under certain circumstances in a certain order. ''Consecutively''.[[/note]] The unlock method has been significantly shortened (but made more luck-based) in ''Afterbirth'': [[spoiler: Die with any character in a Sacrifice Room, while holding the Missing Poster. The difficulty is now getting both items to appear in a run, since seeded runs do not work.]]

to:

** Unlocking [[spoiler:the Lost]] would be a tall order for any one player to accomplish using only the resources made available in game, so much so that the process was ultimately figured out by some people data mining and spoiling it; this unsurprisingly prompted an upset response from creators Edmund [=McMillen=] and Tyrone Rodriguez, who noted it was meant to prompt an [[AlternateRealityGame ARG]]-type response with the community working and speculating to solve it. The process was meant to be a community effort, which probably would have worked eventually, but it is still fairly obscure. You either need to spend a long time going in circles and following vague clues to figure this out, though it should be noted that knowing what to do isn't [[SelfImposedChallenge half]] [[MoonLogicPuzzle of]] [[NintendoHard it.]] [[note]]To put it in perspective, the process involves dying in a certain room holding a certain item in order to receive one part of four images that hint at the actual unlock process, which involves dying with four certain characters in certain locations under certain circumstances in a certain order. ''Consecutively''.[[/note]] The unlock method has been significantly shortened (but made more luck-based) in ''Afterbirth'': [[spoiler: Die with any character in a Sacrifice Room, while holding the Missing Poster. The difficulty is now getting both items to appear in a run, since seeded runs do not work.]]]] However once you unlock them, you can use them in any run afterwards.
11th Jun '17 7:47:20 PM DastardlyDemolition
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** In ''Afterbirth '' there is the True ''True'' Final Boss in the [[TheVeryDefinitelyFinalDungeon Truly Final Dungeon]], [[spoiler: Delirium]].
4th Jun '17 2:07:17 PM nombretomado
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** The Placenta item from ''Rebirth''. It immediately gives an extra heart container on pick-up, and will slowly restore your health... at a rate of half a heart every few minutes. If you're low on health and have exhausted every other option, this item lets you gradually regenerate to full health just by leaving the game on for half an hour or so while you physically get up and do something else to pass the time. (No, TvTropes is not an option unless you have another device; clicking out of the game pauses it.)

to:

** The Placenta item from ''Rebirth''. It immediately gives an extra heart container on pick-up, and will slowly restore your health... at a rate of half a heart every few minutes. If you're low on health and have exhausted every other option, this item lets you gradually regenerate to full health just by leaving the game on for half an hour or so while you physically get up and do something else to pass the time. (No, TvTropes Wiki/TVTropes is not an option unless you have another device; clicking out of the game pauses it.)



-> [[TvTropesWillRuinYourLife Today I died]]. I was killed by this page on [[Main/TvTropes some wiki]]. (ugly)

to:

-> [[TvTropesWillRuinYourLife Today I died]]. I was killed by this page on [[Main/TvTropes [[Wiki/TVTropes some wiki]]. (ugly)
20th May '17 11:16:54 AM greatpikminfan
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* ChestMonster: ''Afterbirth+'' added a chest type that looks normal but becomes spiked when you stand right next to it.

to:

* ChestMonster: ''Afterbirth+'' added a chest type that looks normal but becomes spiked when you stand right next to it. After some complaints, the chests were redesigned so that the difference between them and standard brown type was more obvious.



* ColorCodedForYourConvenience: Champion enemies have traits based on their suit of color, and all of them do one heart of damage rather than half. Grey means an enemy [[MadeOfExplodium explodes]] at death and drops a bomb, red means [[DamageSpongeBoss massive HP]] and possible regeneration with a heart drop, black drops a key, blue means it explodes into bullets on death, green leaves a trail of green creep and drops a pill, and pink generally means "less dangerous, but can still hurt you".

to:

* ColorCodedForYourConvenience: Champion enemies have traits based on their suit of color, and all of them do one heart of damage rather than half. Grey Dark green means an enemy [[MadeOfExplodium explodes]] at death and drops a bomb, pale red means [[DamageSpongeBoss massive HP]] and possible HP]], dark red means regeneration with a heart double-heart drop, black gray deals double damage and drops a key, light blue means it explodes into bullets on death, green leaves a trail of green creep and drops a pill, and pink dark blue generally means "less dangerous, but can still hurt you".you" and gives friendly flies.



* HitboxDissonance: The wall-crawling spider type enemies have a damage hitbox that's extremely confusing, placed at least an inch away from the front of the actual model. Since this hasn't been fixed and the crawlers are often protected by a pit, this could be intentional to keep the game from becoming unwinnable by having extremely low range. Still, this can be frustrating when Brimstone and diagonal shots like tiny planet don't hurt them despite visibly touching them.

to:

* HitboxDissonance: HitboxDissonance:
**
The wall-crawling spider type enemies have a damage hitbox that's extremely confusing, placed at least an inch away from the front of the actual model. Since this hasn't been fixed and the crawlers are often protected by a pit, this could be intentional to keep the game from becoming unwinnable by having extremely low range. Still, this can be frustrating when Brimstone and diagonal shots like tiny planet don't hurt them despite visibly touching them.them.
** This can happen to Isaac himself through size-altering pills. "One Makes You Larger" does ''not'' increase the size of Isaac's hitbox, but it does increase his visual size. "One Makes You Small" ''does'' decrease Isaac's hitbox along with his size.



* MarathonLevel: The new VeryDefinitelyFinalDungeon, [[spoiler:the Void]], is this. It's as large as two XL Womb floors put together and has 6 or 7 boss rooms besides the FinalBoss fight. Good luck finding your way there if you get hit by Curse of the Lost.

to:

* MarathonLevel: The new VeryDefinitelyFinalDungeon, [[spoiler:the Void]], is this. It's as large as two XL Womb floors put together and has 6 or 7 boss rooms besides the FinalBoss fight.fight, one of which always contains another "final" boss. Good luck finding your way there if you get hit by Curse of the Lost.



* NintendoHard: A "hard" difficulty level has been added, which significantly dials up the amount of enemies and [[EliteMook champions]] while giving you less powerful items.

to:

* NintendoHard: A "hard" difficulty level has been added, which significantly dials up the amount of enemies and [[EliteMook champions]] while giving you less powerful items. ''Afterbirth+'' does this for Greed Mode, which is called Greedier Mode.



* ThemeNaming: The {{Disc One Final Boss}}es [[spoiler:and the True Final Boss]] all have boss themes that end in ''cide''. (''Matricide'', [[spoiler:''Ventricide'', ''Hericide'', and ''Infanticide''.]] Averted with the [[spoiler:fake]] {{True Final Boss}}es, who have uniquely named themes ([[spoiler:''Ascension'' and ''The Fallen Angel'']])

to:

* ThemeNaming: The {{Disc One Final Boss}}es [[spoiler:and the ''Rebirth''[='=]s True Final Boss]] all have boss themes that end in ''cide''. (''Matricide'', [[spoiler:''Ventricide'', ''Hericide'', and ''Infanticide''.]] Averted with the [[spoiler:fake]] {{True Final Boss}}es, who have uniquely named themes ([[spoiler:''Ascension'' and ''The Fallen Angel'']])



* UniqueEnemy: There's a blue-skinned variation of the Conjoined Fatty monster that has a very slight chance of appearing in the I AM ERROR room and [[spoiler:the Chest]]. Despite what its appearance may imply, it's completely distinct from a champion variant and attacks with vicious homing Ipecac shots.

to:

* UniqueEnemy: UniqueEnemy:
**
There's a blue-skinned variation of the Conjoined Fatty monster that has a very slight chance of appearing in the I AM ERROR room and [[spoiler:the Chest]]. Despite what its appearance may imply, it's completely distinct from a champion variant and attacks with vicious homing Ipecac shots.


Added DiffLines:

** Two Stone Grimace varieties are extremely rare and only appear in one floor. One is the Broken Gaping Maw, which alternates between trying to suck the player character in with more force than the normal Gaping Maws and not doing anything, found only in [[spoiler:the Womb]] and neither of its alternate floors. The other is the Brimstone Grimace, which fires brimstone lasers and can only be found in [[spoiler:Sheol]]. It is possible to play the game for a long time through several runs without even seeing either of them.
1st May '17 8:58:07 PM intastiel
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* KillEnemiesToOpen: Every room containing enemies will automatically shut itself down until you kill them all. However, the game also features a twist to it, as it's possible to force your way out of a room containing enemies by blasting the door with a bomb. (Either yours or fired by an enemy). Of course, this tactic must be used sparingly because bombs are a precious commodity most of time, and doing so doesn't take care of the enemies inside the room, so if you walk back into it, you'll either have to deal with the enemies, or use another bomb to escape once again. Also, this tactic doesn't work in boss' (nor mini-boss') battles, because their doors are blast-proof... [[spoiler:Just like every single door in the game's BrutalBonusLevel.]]
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