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A list of characters who appear in The Binding of Isaac. Currently under construction, please contribute!
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A little boy who gets thrown in the basement and must fight for his life against a never-ending assortment of demons and mutants, the alternative being his mother killing him. Beating the game in certain ways or collecting certain items unlocks variations of Isaac with their own unique attributes.
The Antichrist: The definitive true ending of Rebirth shows that Isaac was the anti-Christ, the voice his mother heard really was the voice of God telling her to kill him. And by defeating Mega-Satan, you prove to him that you're worthy to be his champion and Isaac is turned into a demon.
Create Your Own Villain: Well, antagonist. Isaac would never have been forced to kill his own mother if she hadn't snapped and tried to sacrifice him in the first place. Gains some very interesting implications at the true ending of Rebirth where it's revealed that Isaac becomes a demon or the Anti-Christ inside the Chest. Did Isaac have darkness inside him all along or did he decide Then Let Me Be Evil after the horror that he went through?
Dark and Troubled Past: The horrible memories of things that Isaac suffered through are relived in level loading screens. In one ending, the photograph montage of Isaac's past leaves a lot of interpretation as to what happened to his family, namely what happened to his father (who likely left, went missing, or died).
Dead All Along: After beating It Lives for the tenth time and unlocking Ending 10, Isaac comes across his corpse stuffed into a chest. At least one interpretation of this involves Isaac having been dead the whole time. The next three endings explore the events leading up to his death in reverse chronological order, first showing him willingly locking himself in the chest, then showing his self-loathing which led to this, and finally showing his tragic backstory through a heartbreaking Photo Montage.
Enemy Without: The boss of The Cathedral Isaac seemingly fighting himself and the boss of The Chest is ???, which was strongly implied to be a dead Isaac post-suffocation and cyanotic.
Then Let Me Be Evil: It is strongly implied that at the ending of Rebirth, Isaac becomes a demon or the anti-christ in order to deal with all the horror he went through, up to and including his mother.
Acrofatic: Several items make your character fatter, and most don't negatively impact speed. Combine these with items that increase your speed and you have this trope.
Badass: Badass enough to kill Satan, in both his normal & most powerful forms.
Blessed with Suck: Guppy's Tail makes you finds golden treasure chests more often. This comes at the expense of keys needed to open those chests, though if you're lucky the chests cough them up. Works wonders with an Skeleton Key or a Flat Penny.
Made potentially worse or better with The Left Hand item that changes all chests to Red Chests. They don't require a key to open, but half or more of the things that come out of a red chest is not something you want (including enemies and troll bombs).
Body Horror: Most of the powerups mutilate the character in some horrific way.
Bullet Hell: It's possible to get a character that shoots a four-way bullet spread at the speed of a machine gun with additional single shots from the other three cardinal directions.
Collision Damage: Isaac takes damage from pretty much everything that moves. The player can cause this if they use My Little Unicorn (or the Chariot tarot card) or the Virus powerup. The former is temporary, while the latter is permanent but doesn't prevent damage in return.
Cross Dresser: The alternate characters are all Isaac wearing different costumes, meaning that he is this when dressed as Eve or Maggy.
Dark Is Not Evil: An Isaac with a lot of Devil items is still just looking to survive.
Flight: Plenty of items, both permanent and temporary. You can become an angel, a demon, an angelic ghost, a demonic ghost, a floating head, and a cat (which somehow flies). All of these let you pass through rocks and over pits.
Becoming possesed by Guppy (the flying cat form) alows you to fly because why couldn't a possibly demonic cat possesion also allow you to fly. Also it's a kitty cat.
Full-Frontal Assault: Before the events of the game, his clothes were taken away from him as part of Mom's attempts to remove the evil around him. In most playthroughs, he fights his way through monsters naked.
Collecting three Guppy items (Dead Cat, Guppy's Tail, Guppy's Paw or Guppy's Head) will transform the player character into Isaac's pet cat. Doing so unlocks a new item (the first time), gives you flight, and applies the effect of the Mulligan.
In Rebirth, the same is possible with "Lord of the Flies", activated by finding three fly-related items.
Took a Level in Badass: Throughout the game, if the right items are acquired. Isaac starts the game as a crying child and can potentially end it as a flying demon that can demolish bosses in seconds with giant lasers.
Named after the biblical son of Abraham, is playable from the start and has no defining accessories. According to Edmund McMillan, he represents the fighter class of traditional games and begins with no items.
Badass Normal: He's the only playable character that starts off without any sort of supernatural assistance. Even the D6 is merely a six-sided die.
Master of None: Gets no starting item to work with, unlike the others. Unless you unlocked the D6.
Debut: The Binding of Isaac
Named after a friend of Mary, the mother of Jesus, she is distinguished from Isaac by blonde hair and bow. Maggy represents the cleric class from traditional games and starts with the Yum Heart: an activated item that restores one heart upon use.
Boring but Practical: Her gimmick is somewhat bland compared to the others, but having 4 red hearts to work with allows for Devil Room deals early on without severe consequences. Additionally, the Yum Heart restores a red heart every 3-4 rooms or so, which keeps her healthy and can be a godsend during the later chapters.
Stone Wall: Starts with low speed and 4 hearts, the highest starting amount possible, and a healing item.
Taken Up to Eleven in Rebirth during "The Tank" challenge. Maggy now starts with seven heart containers, the Yum Heart, and the Infamy mask, which blocks (some) damage from the front. Unfortunately, she now runs slower than even some enemies, making dodging difficult, if not impossible.
Named after the biblical son of Eve and first murderer, he is distinguished from Isaac by an eyepatch. He represents the Thief class from traditional Role-Playing Games and starts the game with the Luck Foot: a passive item that improves random events in various ways.
Born Lucky: Cain's starting item gives him increased luck in certain situations.note Pills will never have negative effects, Rewarding Vandalism is more likely to happen, the odds of winning the Skull game increases from one-third to one-half, and gold chests are more likely to give items (as opposed to pickups).
The Dev Team Thinks of Everything: For most characters, Technology 2 stacks the beam on top of their tears. Cain's the exception, his tears being shut off due to his eyepatch. Chemical Peel is changed, too; while with other characters every other tear will have increased damage due to one half of the face being scarred, with Cain, every tear has a 50% chance of dealing increased damage.
Fragile Speedster/Glass Cannon: Starts with great speed and attack and an average rate of fire but suffers from low range and health. Outright called "the thief" by the art booklet. Being "the thief" could be considered Fridge Brilliance considering he "stole" his own brother's life in the Biblical story of Cain and Abel.
Nerf: His speed and damage got hit with the nerfbat for Rebirth, and the mechanics of Lucky Foot changing also indirectly hurt him.
Debut: The Binding of Isaac
Named after the first woman and original sinner, Eve is distinguished from Isaac by long dark hair and eyeshadow. Representing the druid class from traditional games, she starts with The Whore of Babylon, which turns her into a demon at low health, and the Dead Bird, which fights for her when she is damaged.
Cast from Hit Points: The Dead Bird is activated by taking damage in a room and works as a faster level three Meat Boy for the room in which it activates.
Combat Sadomasochist: Both of her starting items (and the items she can unlock) are Cast from Hit Points, and she is the only character who doesn't leave a puddle of urine upon entering a room with half a red heart.
Critical Status Buff: When she's down to half a heart, her Whore of Babylon powerup grants her greatly increased attack.
Rebirth gives her an extra buff, activating Whore of Babylon at one full heart instead of a half one.
Crossdresser: It is implied heavily that Eve is just Isaac with a wig and makeup.
Named after the disciple who betrayed Jesus, he has a fez to distinguish himself from Isaac. He represents the mage class from RPGs and starts the game with the Book of Belial, an activated item that increases attack power for one room. In the original game, he unlocks after beating the Womb for the first time. In Rebirth, he unlocks after beating Chapter 5 for the first time.
Glass Cannon: More so then Cain. Starts with average rate of fire, range, speed and high attack power, further bolstered by his Book of Belial. In exchange, he starts with only 1 heart.
Deal with the Devil: While holding the Book of Belial, the chances of a Devil Room appearing are increased. Unfortunately, Judas' starting 1 heart makes it impossible to make deals unless he gets more heart containers or soul hearts.
Difficult but Awesome: Starts off with the most consistent damage of all the playable characters (Eve and Samson's powers are conditional), but with only one starting heart and average speed for dodging, you don't have much leeway to screw up.
Nice Hat / Take That: Judas' fez, which doubles as a jab at Phil Fish, who voted against Edward Mcmillen and his comrades at the Independent Games Festival, which made him a Judas (ergo, a traitor).
The Take That part is actually subverted. Edmund has stated that he just needed an iconic hat for Judas, and went with the idea of Fish representing Judas because he found it funny.
Squishy Wizard: The artbook refers to him as the "mage", fitting in the other RPG archetypes. It fits since Judas has high starting damage (especially with the Book of Belial active) but very low starting HP.
Debut: Wrath of the Lamb
Introduced in Wrath of the Lamb and named after the biblical strongman, he has long, brown hair and Big Ol' Eyebrows. He also starts with a red headband called Blood Lust, which grants him a temporary but substantial attack-power boost for each enemy he kills in the current room. This is fitting with the fact that he represents the Berserker class.
Blood Knight: His trademark power-up is called Blood Lust, after all!
Conservation of Ninjutsu: Invoked by his special hair-band. The more enemies you face in a room, the more powerful you'll get! But single target rooms won't trigger any attack-boost.
Critical Status Buff: In Rebirth, Bloody Lust makes Samson deal more damage as takes damage, with him reaching near maximum damage for having taken several hits in a row. In this case he literally Turns Red to reflect Bloody Lust activating.
Difficult but Awesome: Blood Lust makes Samson powerful... if you manage to survive the hordes of enemies that give him his strength.
Glass Cannon: With just 1 starting heart container, he's as fragile as (and under some circumstances, even more than) Judas. However, his special gear makes him extremely effective against large groups of enemies and/or mook makers.
Power-Up Letdown: He's probably the most difficult character to unlock (with ??? possibly being more tedious than difficult), as it requires you to pass on 2 free items on a regular run... and it's capacity is dubious to say the least. After months of complaints, Edmund promised a buff to Samson. The buff was starting with a soul heart on top of his single regular heart. He became much more useful in Rebirth, as he now starts with three regular hearts and his buffs from killing enemies and taking damage remain until you leave the floor. On the other hand, he became even more difficult to unlock, as he now requires you to clear two floors in a single run without taking any damage.
Took a Level in Badass: In Rebirth, Samson starts with a much more forgiving 3 hearts and gets to keep his buffs until he leaves that floor. This is a major improvement from his previous incarnation.
Debut: The Binding of Isaac
Click here for the picture
Unlocked after defeating Mom's Heart/It Lives ten times, ??? is a shout-out to Edmund McMillen's Newgrounds account (specifically his "Dead Baby Dressup" game). Starts with ThePoop, which creates a pile of dung once per room. Whilst his official name is ???, his nickname is "Blue Baby", which is how he signs his death note on the Game Over screen (and how he's listed on the PSN Trophies list for Rebirth).Despite being a Joke Character gameplay-wise, he is possibly one of the most plot-relevant characters in the game. His reveal indicates that the vignette of Isaac suffocating in the chest is canon, and not only that, but he somehow died of asphyxiation whilst there. At this point it is implied that Isaac has been Dead All Along and Endings 11 and 12 seem to indicate that Isaac actually locked himself in the chest after being Driven to Suicide.
Not Quite Dead: His gimmick is being able to resurrect instantly, rather than outside the room he died (forcing him to restart it).
Power-Up Letdown: His extra life only resurrects you with exactly one heart container, and only gives you a blood trail for the current room if you get hit once. On the other hand, it does resurrect you on the spot (unlike the other extra lives that return you to the previous room), possibly allowing you to finish off whatever killed him.
Close Range Combatant: The closest thing that Rebirth has to one, since his starting weaponry forces him to get relatively close to enemies. He compensates by possessing above-average speed and flight.
Disc One Nuke: His flight and Brimstone are a major advantage in the early game, and flight remains an important bonus throughout.
Dungeon Bypass: Possessing flight lets him ignore spikes, rocks, and other terrain right from the start. Rather useful.
Fragile Speedster/Glass Cannon: Fast, possess flight, and has high starting damage, but at the cost of poor range that cannot be increased and having to charge Brimstone for attacks. His black hearts damage everything if one gets depleted and he can eventually gain red heart containers through Health Up items, but he is in overall much frailer than characters who can pick up red hearts from the get-go.
Hit-and-Run Tactics: Unlike others who depend on kiting with tears, Azazel often has to fly in, blast several enemies with brimstone, then get out of there before the rest retaliate.
The Last of These Is Not Like the Others: Azazel is by far the most different from the other playable characters, since he starts with miniature brimstone instead of tears, has evil hearts (but can gain red ones, unlike ???), and has flight (which only The Lost shares). The result is a rather different playstyle, including item selection, since his smaller brimstone makes many items useless/redundant but others extremely powerful.
Required Secondary Powers: A melee character would've been an interesting addition to the roster, but an actual melee attack would make multiple rooms Impossible By Design. Azazel being equipped with the piercing brimstone and flight fixes both of these problems.
Named after the biblical garden, Eden's stats are randomly generated every time you play as them. Their gender is undefined, and to play as them requires the use of one "Eden token", earned by beating Mom's Heart. Unlocks in Rebirth after beating the Womb for the first time.
Anime Hair: The hairstyle is random, and many options look like this. The color is always white.
Confusion Fu: Always starts with a random set of items and stats.
Eden isnt a man, nor are they a woman.. they just are.
Click here for the picture
A ghost character, and one of the only characters not based off of any sort of religious contextnote unless it refers to the "souls lost in Limbo", next to ???. It is the secret character of Rebirth, and has a very complicated unlock process.
Chekhov's Gunman: Actually, it appears several times prior to being unlockable, albeit so briefly that few players would actually notice. Specifically, it is the ghost that departs from Issac every time he dies.
Glass Cannon: And how! It has zero health and can't gain any type of hearts, period. The only upside to this is that it take Devil Room and Angel Room upgrades for free, possibly resulting in a One-Hit-Point Wonder powerhouse early on.
Guide Dang It: Unlocking it is a bit...convoluted. First, you need to let yourself get killed by a Mulliboom in the basement as Isaac. Next, you need to blow yourself up with one of your own bombs as Maggie in the caves, then let yourself get killed by Mom's foot as Judas. Finally, you need to let yourself die to Satan on the second phase of his fight as Azazel. And you need to do all of this in a row. Mess up once and you have to start all over again. Not very easy, to say the least, although the at the very least you get (cryptic) hints as to the next step once you've completed one.
Joke Character: Starts with the ability to fly, with the downside of having absolutely no HP.
Lethal Joke Character: Its lack of HP means that it can take Devil items (some of the most powerful items in the game) for no cost at all. Normally it would cost one or two heart containers for one of those items.
One-Hit-Point Wonder: Dies in one hit from anything. Earlier versions had him die from continuing a run.
Power Up Letdown: Remember how some thought that Samson and ??? weren't worth the effort it took to unlock them? The Lost is quite possibly even worse in this regard, especially since unlocking it involves a dose of Guide Dang It too.
Bullet Hell: Leapers shoot bullets in all four cardinal directions when they jump. If five end up in a room, be prepared to dodge.
Elite Mooks: Fire Hoppers and Leapers, the former being stronger and the latter shooting bullets. It should be noted that fire hoppers cannot spawn by themselves, Hoppers have to touch fire first.
Infernal Retaliation: Hoppers move twice as fast, jump twice as far, and inflict more damage when they're on fire.
Violation of Common Sense: Not only does every other enemy (or character, even) take damage themselves from fire, but Isaac's main combat strategy is attacking enemies with water. Despite that they seem to have double health.
Elite Mooks: The Evil Twin. Instead of looking like a meat puppet, it looks like a demon that can: fly, shoot a three spread, and do more damage. Good things is that its bullets travel slower, giving you time to dodge and shoot.
Enemy Without: They mirror the player's movements, including shooting, but most rooms come with a mechanism with which to destroy them. There are also bombs, and praying that whipped shots will work.
Foreshadowing: The appearance of these foreshadows the nature of Isaac the boss.
Classic Video Game Screw You: It's uncommon, but this guy can be the boss of ANY dungeon save ones with predetermined bosses. He's notorious for showing up in the Basement/Cellar, often before you've had a chance to buff your speed and survive his charge.
Degraded Boss: In Sheol. He's later fought at full strength when the Satan fight begins.
Early Bird Boss: He can replace any boss that's not pre-set by the level. If you're unlucky he can appear on the first or second floor...
The Dragon: To Satan. He even acts as the first stage of his master's boss fight!
Palette Swap: Of The Fallen, except he doesn't split into two parts, and he has a special attack (which can be obtained in Rebirth through one of his drops, the "Head of Krampus").
A secret boss in Rebirth, a fight with one of three Angels is initiated by bombing the statue in an angel room at any point throughout the game. Beating the boss twice unlocks a piece of a key each time, and doing so allows the player to unlock the true final boss of the game.
Guide Dang It: Bomb the angel statue in an Angel Room to provoke it into a fight. Less aggravating than other examples since there are more in-game clues and it is often next to blue fires, so the player at least has an incentive to place a bomb nearby.
Hidden in Plain Sight: A fight can be initiated at any point in the game, provided you have beaten either ??? or The Lamb.
The four Horsemen of the Apocalypse, unlocked after beating Mom for the first time. Famine, Pestilence, War and Death each have the ability of replacing one of the bosses of the Basement, Caves, Depths and Womb respectively, while the Headless Horseman has the capability to replace any of these bosses, and Conquest was introduced as an alternate boss to Death.
All Your Powers Combined: The head has Famine's triple shot and War's triple charge, while the body is Pestilence minus spawning enemies. Plus, you fight two bosses at the same time, which is what happens when Death loses half his health.
Continuity Nod/Genius Bonus: invoked The secret calls him "A Forgotten Horseman", reflecting the fact that he's been replaced by Pestilence both in the game and in nearly every other version of the Horsemen of the Apocalypse. Also, it was replaced because it was too similar to War. Conquest has improved versions of War's attacks.
Bandit Mook: His shots (and mere contact with him!) take away a couple of pennies from you, while making you drop a variable amount on the floor that you can try to retrive... Just be careful while doing so, if you don't want to be killed in the process. Oh! And guess what? His mook-lookalikes have the same ability as him. Yay!
Breakout Character: He's the most memorable and ubiquitous of the The Seven Deadly Sins mini-bosses, and Wrath of the Lamb cemented his status by adding a quite a few new versions of him.
Chest Monster: Replaces shops and secret rooms. He's more likely to appear as you go further in the game.
Expy: He shares some traits with Spelunky's Shopkeeper, including his multi-shot ability, potential to turn hostile on the player without previous warning, and overall dickishness.
King Mook: Wrath of the Lamb added Super Greed, who is bigger, meaner, scarier, and can spawn Greed-heads. Said Greed-heads also appear in the Depths, the Catacombs, and the Necropolis.
Mook Promotion: Inverted. The game's standard version features him as a mini-boss, but the expansion added mook-versions of him that share some of his most aggravating attributes.note Multi-shot and, most importantly, the ability drain your money.
The Scrappy: Invoked. Given how he can replace shops and secret rooms, can knock out your money when he hits you, and can be fought multiple times in one run, players usually don't enjoy finding him.
Hoist by His Own Petard: Wrath's bombs can be pushed around like player-dropped bombs, allowing you to push them back towards him for a nice chunk of damage. This doesn't work on Super Wrath's troll bombs, though. Even more amusingly, any items that affect bombs will affect the bombs dropped by Wrath/Super Wrath. This can result in hilarious situations where, if you have the Bobby-Bomb collectible, every bomb the boss drops proceeds to walk back toward him.
Mook Maker: As its name implies, it creates flies.
Taking the Bullet: Spawned flies circle the Duke for a bit before coming after you, letting them soak up your shots.
Debut: The Binding of Isaac
Bullfight Boss: The big one can tire out after a few moments of running. If the big one is killed first, then the small one will turn red, give chase, and never tire out. Steven's little version will do that before the big one goes down.
King Mook: As of Wrath of the Lamb, smaller enemies similar to it appear.
Warm-Up Boss: Shares this with Monstro, but which boss is the easier of the two if any is up to personal opinion.
Debut: Wrath of the Lamb
Body Horror: She's made out of a head with four eyes, leg bones, and toes.
Flunky Boss: Not only does she spawn spiders directly, but she can also spawn Mook Maker spider silk Boils! And that's not even getting into the ones that can spawn bigger Asteroids Monster spiders or other kinds of Boils.
Word of God: Edmund has stated that the Widow is a girl.
Debut: Wrath of the Lamb
Back from the Dead: Inverted: Pin was introduced in the Wrath of the Lamb as a weaker, living version of Scolex.
Tactical Suicide Boss: Is not immune to its green exploding projectiles, and due to a quirk in hit detection, can actually damage itself with them when it begins to bury underground. The dark grey one averts it, replacing the bombs with bullets.
Debut: Wrath of the Lamb
Dual Boss: The blue version is two smaller Gurdy Jr.'s.
Not-So-Innocent Whistle/Enemy Summoner: He occasionally will whistle innocently (complete with a music note hovering above his head), before one to three Squirts appear beside him to fight.
Flying Face: That rips itself open to reveal a skull when its minions are dealt with.
Flunky Boss: Before actually fighting you, he will always summon three smaller ghosts.
Good Bad Bugs: He is vulnerable for a tiny period of time before sending its minions after you. Sufficiently broken characters can kill it in this window!
No Fair Cheating: He normally paces from side to side along the top edge of the screen, shooting downwards. If you try to avoid the shots by approaching the top edge of the screen yourself, it dash in an attempt to bump into you.
Degraded Boss: Interestingly, the weaker version attacks very differently, charging and firing circular waves of bullets. Contrast with the other bosses made into minibosses, who are more or less identical to their original version, but weaker. Wrath of the Lamb separates the degraded form into a different boss: Gurdy Jr. But The Very Definitely Final Dungeon DOES feature Gurdy as a normal Degraded Boss.
Back from the Dead: Gemini is now a zombie, and is accompanied by his conjoined brother's ghost. The image appears to be more of a sperm and an egg. That wouldn't discredit this trope, it would just be a different set that came back, because at least the large one is undeniably dead no matter what perspective you look at it from.
Word of God: Edmund has stated on his Formspring that the Mask is female, and the thing inside is not alive.
Daddy Long Legs/Triachnid
Daddy Long Legs/Triachnid
Debut: Wrath of the Lamb
The Cameo/Mythology Gag: Triachnid is a reference to a previous flash game by Edmund McMillen. Furthermore, Triachnid is an alternate of Daddy Long Legs; in his own game, Triachnid was finding a home for his young.
Dummied Out: As hinted here, Triachnid was originally was cut before the game was released. It wasn't removed entirely, though. Due to a glitch, it originally would replace the Cathedral's True Final Boss. This was eventually corrected, and Triachnid was added in as a normal boss.
The Dev Team Thinks of Everything: There is an item that summons the Daddy Long Legs to stomp enemies in an area the player is standing in without hurting them. Using this against the Daddy Long Legs reskins it as the Triachnid's claw. Using it against Triachnid flat out doesn't work.
Back from the Dead: He is the post-humous version of the Dark One, covered in bandages and with a shattered horn.
The Bad Guy Wins: It's revealed that Isaac suffocated to death while inside the chest. She wanted Isaac to die because of an (alleged) order from God, do the math. However, subsequent endings revealed that Isaac locked himself in the Chest before the events of the game, and Rebirth's Ending 15 shows what appears to be her grieving for Isaac, so this is probably a subversion.
The Extremist Was Right: She's a religious fanatic that appears to think that she's on a mission from God, which is clearly not the case. At least until the canonical end of Rebirth, strongly implying that Isaac either was or now is a demon. If you subscribe to the "just batshit insane" theory, then she's Right for the Wrong Reasons.
Body Horror: The way Mom's body parts move throughout the fight (such as both eyes appearing on opposite sides of the room while she tries to stomp on you) suggest an ability to contort herself in rather...impossible ways.
Evil Laugh: She lets out one every time she successfully damages Isaac.
The Faceless: Her entire face is never shown at any point in the main game (the intro and epilogue don't count, as they're Isaac's cartoon drawings). This is subverted in Wrath of the Lamb, but only near the very end, and only briefly. In photographs, to be precise.
Fan Disservice: When Isaac uses the Mom's Bra item, a picture of his mother's shirtless torso flashes on the screen. A very unflattering picture of his mother's less-than-fit shirtless torso.
Humanoid Abomination: Most of what she does in-game and in a few cutscenes blatantly disregards normal body movements if not physics. She can step on her own eye, generally alter size, and her arm can fit in a chest inside her heart inside her womb.
Leitmotif: Thine Wrath... in the original, Matricide in Rebirth.
Your Size May Vary: Just how big is she? In the cutscenes, she's a normal-sized human being, but her underwear is the right size to be worn by a child visibly smaller than her, in the boss fight her leg is the length of the screen, and then her womb is big enough to have two entire levels in it, with her heart being larger than Isaac.
Body Horror: Like Fistula, it's named after a real life Body Horror phenomenon in which the body forms a growth containing all three germ layers... one of which can potentially manifest as bone shards and teeth!
Wall Master: She can hide in the walls of the boss room, immune from damage.
Giant Mook: A giant boss version of the enemy Fred that appears in Chapter Four.
Mom's Heart/It Lives
Click here for the picture
The final boss of the fourth chapter, and the initial final boss of the game overall, after traversing the Womb, Isaac is forced to fight his mother's still-beating heart. Beating it is what unlocks Endings 1-10 (or 1-11 in Rebirth). After reaching Ending 9 (11 in Rebirth), Mom's Heart is replaced by a new boss: It Lives, Isaac's fetus.
Leitmotif: ...Be Done in the original, Ventricide in Rebirth.
Mook Maker: Hides at the back of the room while it spawns normal enemies to fight you, then jumps back to the centre to spawn more.
Nerf: Inverted; both bosses are made much harder in Rebirth.
Not Quite Dead: It seems that Mom survived their fight, or at least her heart did.
True Final Boss: Was initially this to Mom's Final Boss. However, this is subverted by the Halloween update, and further subverted by Wrath of the Lamb and Rebirth, to the point that it's no longer anywhere near the real final boss.
Chapters Five and Six: Sheol and Dark Room
Click here for the picture
Debut: The Binding of Isaac
The original True Final Boss (although this isn't true as of Wrath of the Lamb and Rebirth), Satan himself is the boss of what was originally the game's secret floor. Despite offering Deals with the Devil throughout the game, he turns on Isaac, and tries to kill him. His boss fight is comprised of three phases, detailed below under Sequential Boss.
Black Speech: During the fight with him, he sounds somewhat like this. They're actually Mom's quotes, played backwards and in a much lower tone.
Bragging Rights Reward: Besides unlocking the final and definitive ending, there is no reason to fight him other than to boast you did it. The only thing you get out of winning is a new picture for your save file. There are no associated item or character unlocks, not even a mark on the character file to indicate that character beat him.
Final Boss Preview: Regular Satan's third phase can be considered this. In Sheol, you only fight his lower half. In the Chest/Dark Room's secret room, you face the much more difficult upper half.
Flunky Boss: Summons The Harbingers, the Super Sins, and fallen versions of the Angels.
Guide Dang It: The only in-game hint you have to his existence is "The Angels await!." You're supposed to bomb the Angel statues in the Angel Rooms, prompting them to engage you; both will drop a piece of a Golden Key on defeat, and getting both pieces opens a Golden Door in the Chest/Dark Room that leads to Mega Satan.note The Golden Door also only appears if you have the completed key to begin with, which is a Guide Dang It in and of itself.
Fortunately, completing the key also unlocks "Dad's Key" as a regular item, which can also be used on the Golden Door for future playthroughs.
Soundtrack Dissonance: Due to a bug, doing too much damage to any form will cause the calm, somber "boss defeated" music to start playing.
True Final Boss: The very definitive True Final Boss of the game (which is saying something, considering there have been seven other candidates before it), having an extra unlock process required each run.