History Main / BonusDungeon

* The Hellgate from ''VideoGame/TacticsOgre'' was 100 levels deep, and interestingly actually tied into the plot, as the bottom level was where one of the {{Superboss}} villains in the game had retreated to. Beating him didn't change the main plot of the game, though. In order to get the ultimate "bragging" item in the game, one had to go through the Hellgate twice, as well as get 4 specific weapons from special encounters with recolored monsters.

* ''VideoGame/FireEmblem'': ''[[VideoGame/FireEmblemTheSacredStones The Sacred Stones]]'' has two of these: the Tower of Valni, and, more fitting, as it is only available toward the end of the main game, the Lagdou Ruins.
* ''VideoGame/FireEmblemGaiden'' has one in its remake, ''Echoes: Shadows of Valentia'', in the form of the [[RuinsForRuinsSake Thabes Labyrinth]], a ten-level dungeon unlocked in a special "Act 6" after beating the FinalBoss and accessing the clear save data. Story wise, the Labyrinth chronicles the story of an alchemist named Forneus [[spoiler:and the origins of the Fell Dragon Grima, the BigBad of ''VideoGame/FireEmblemAwakening'']]. Gameplay wise, it is extremely [[BrutalBonusLevel brutal]]. [[CheckpointStarvation The entire dungeon doesn't have a single save point]] (not counting {{Suspend Save}}s) and is filled to the brim with extremely beefed-up mooks. The boss of the dungeon, [[spoiler:Grima himself,]] is even accompanied by {{Elite Mook}}s that would otherwise spawn in extremely rare encounters. Not helping is the boss has an ArmorPiercingAttack and most enemies [[ReadingsAreOffTheScale have much more HP than the HP bar can display]].

* Every game in the ''VideoGame/{{Klonoa}}'' series includes one or more "EX Visions" available after completing the main plot. These are usually much harder than anything else in the game.

* ''VideoGame/DonkeyKongCountry'':
** ''VideoGame/DonkeyKongCountry2DiddysKongQuest'' and ''[[VideoGame/DonkeyKongCountry3DixieKongsDoubleTrouble Dixie Kong's Double Trouble!]]'' both have Lost Worlds that you need bonus coins to enter, and these coins are hidden in the regular levels.
** ''VideoGame/DonkeyKongCountryReturns'': The Golden Temple, which is only accessible after completing the game and clearing all Temple levels in the regular worlds. It only has one level in the Wii version, but it has nine in the 3DS one; all of them are very challenging, and require good reflexes and timing to be conquered.
** ''VideoGame/DonkeyKongCountryTropicalFreeze'': The Secret Seclusion, which requires gathering the relics located in the Temple levels (themselves {{Brutal Bonus Level}}s) to enter, and can only be unveiled after defeating the FinalBoss and clearing the game once. It consists of three exceptionally challenging levels, and completing them unlocks Hard Mode.
* ''VideoGame/DistortedTravesty'' has a number of unusually difficult bonus areas that open up along the way. However, the big one is the Spire of Forgotten Souls, a 100 floor TimedMission[[note]]although you get a time reset and full heal every 5 floors[[/note]] filled with some of the most devilish PlatformHell that the creator could come up with. The {{Superboss}} lurks at Floor 100, as well.
* ''VideoGame/OriAndTheBlindForest: [[UpdatedRerelease Definitive Edition]]'' features the Black Root Burrows and its Lost Grove sub-level, which reveal the backstory of Ori's adoptive mother Naru, and grant Ori two new Ancestral Tree skills, which are also required to access new secrets in the main game for HundredPercentCompletion.
* ''VideoGame/HollowKnight'' has the [[BeehiveLevel Hive]], which has little if any relevance to the story, lacks a local map of its own despite being considered a distinct region on the world map, is only necessary for obtaining a [[HeartContainer Mask Shard]], two [[LivingMacGuffin Grubs]], and the Hiveblood Charm in a [[HundredPercentCompletion completionist run]], and [[GuideDangIt the entrance can be tricky to find if you don't use spells.]]
* ''VideoGame/CopyKitty'' features World 13, a bonus set of levels exclusive to Boki's campaign, featuring unique hell and heaven-based enemies in environments that sharply contrast the rest of the game. The Normal version has blood, bones, and a darker color palette with an EldritchAbomination at the end of a difficult series of levels with downright bizarre powers to copy. On Hard Mode, after [[DoubleUnlock completing a lengthy checklist of achievments]], the levels feature holy-themed enemies with more unique abilities and a truly spectacular {{Superboss}}.

* ''VideoGame/TheTowerOfDruaga'', in the ''Namco Museum Vol. 3'' CompilationRelease on the Playstation, had two secretly unlockable 60-floor towers both harder than the original: "Another Tower" and "Darkness Tower", the latter having many new treasures. The Famicom and UsefulNotes/GameBoy versions had a different "Another Tower."
* ''VideoGame/IttleDew1'' has a couple:
** The Master Cave is home to the game's very hardest puzzles. It even requires you to use techniques you never need anywhere else.
** The Compost Crypt was added after launch in a Halloween update. It features more of a balance between combat and puzzles. Notably, the enemies can't be frozen, making them immune to a cheap [[LiterallyShatteredLives freeze-then-smash]] kill.

* After completing ''VideoGame/{{Aleste}}'', select Continue Game from the title screen to be taken to Round 0, a {{Palette Swap}}ped and compressed version of Round 1. It's a relatively easy level and serves as more of a reward than anything.

* ''VideoGame/{{Ib}}'' has one that's accessible near the end of the game if you've [[NewGamePlus gotten a 'survival' ending on a previous playthrough]]. It doesn't have super-tough monsters, but it does have a ton of puzzles that ding your LifeMeter every time you fail to solve them and you're given only one chance to refill your life meter for the bulk of your stay there.

* ''VideoGame/{{Marathon}} Infinity'' has the [[SeriousBusiness vidmaster]] levels. These levels are accessed through a secret area on the last level, and basically put you in three of the hardest levels of the series (One from each game), pitted against the hardest form of each enemy. The reward: Bragging rights.

* ''VideoGame/MedalOfHonor Underground'' featured a campaign after the main game. Players reprised the role of Jimmy Patterson, hero of the first game, as he stormed the castle of a [[StupidJetpackHitler mad Nazi scientist]]. The castle was replete with...interesting...new enemy types, including attack dogs operating armored vehicles and automatons made from suits of medieval armor. Patterson even constructs his own automaton - a man-sized nutcracker.

* The Ancient Cave in the ''VideoGame/{{Lufia}}'' series has gone from 12 levels (''VideoGame/LufiaAndTheFortressOfDoom''), to 100 levels (''VideoGame/LufiaIIRiseOfTheSinistrals''), to 200 (''VideoGame/LufiaTheLegendReturns'') throughout the various games on SNES and Gameboy.

* ''[[VideoGame/MightAndMagic Might and Magic: World of Xeen]]'':
** After freeing Sandro, the Lich-ruler of Necropolis, you get the key to the game's bonus dungeon, the [[IDontLikeTheSoundOfThatPlace Dungeon of Death]], which requires access to both Clouds of Xeen and Darkside of Xeen to enter. Upon entering the Dungeon of Death, expecting highly difficult end-game enemies... the level is instead completely devoid of any enemies at all. It is actually a giant crossword puzzle.
** Played straight in the lower levels of Dungeon of Death, once the crossword puzzle has been solved. However, level 4, the final level, is very goofy, full of [[DegradedBoss Xeen-Maker Machines]], and the only actual reward for completing it is a silly and utterly pointless Easter egg.
* ''VideoGame/VagrantStory'' has a bonus dungeon called the Iron Maiden. While areas in the game has a map to show which path leads to where, the Iron Maiden map doesn't. There's minimal to no light in the Iron Maiden, and the enemies are much more menacing than usual, and that's [[NintendoHard saying something]]. The boss waiting at the end is the reason why this dungeon is called "Iron Maiden".
* The Abyss in ''VideoGame/{{Wild ARMs 1}}'', ''[[VideoGame/WildArms3 3]]'', and ''Alter Code F''. It was smaller in the first game, but all later incarnations had it at 100 levels deep. It exists in ''5'' as well, along with three other {{Bonus Dungeon}}s, but it's much smaller.
* The Chicken Level in ''VideoGame/DungeonSiege''. Hidden behind a series of riddles and item-gathering quests, this was populated with... well, killer chickens with an extraordinary number of hit points. The level was filled with large amounts of fabulous treasure and hard-to-find items for anyone brave and strong enough to defeat the fowl beasts (pun intended).
* The Cow Level in ''VideoGame/DiabloII'' (and the ''Hellfire'' ExpansionPack for ''VideoGame/{{Diablo}}''), inserted as a response to a rumor from the original ''VideoGame/{{Diablo}}'' that such a place existed. Later, the 1.11 patch introduced an elaborate Pandemonium quest with several bonus dungeons.

** In ''[[Videogame/KingdomHeartsCoded Re:coded]]'' there are no classic tournaments despite Olympus Coliseum being present. Instead, it features a 30-floor labyrinth with turn-based RPG gameplay. Only 5 floors must be completed to advance the plot; the rest is optional. There are also hidden system sectors that only show up after you get your Scan ability to a high enough level, the last upgrade only becoming available after completing the story.
* Several examples from the ''VideoGame/{{SaGa|RPG}}'' series:
** ''[[VideoGame/FinalFantasyLegendII SaGa 2: Hihou Densetsu]]'' (''Final Fantasy Legend II'' in North America) has the aptly-named Nasty Dungeon with single-tile hallways that span multiple screens and lead to dead ends and monster encounters the party cannot run from. Naturally the strongest weapons and equipment in the game are found here.
** The Netherworld, Auldburg, Trials of Elore, Jewel Beast's Lair, Purgatory, and Shadow Palace in ''VideoGame/RomancingSaga''. You only need to visit one of the first 3 that are mentioned in order to progress the story, You can open up all three before starting the endquests, but [[spoiler: after completing Auldburg or The Netherworld, you cannot access the Trials of Elore.]]
** ''VideoGame/RomancingSaga2'' has several: the Ice/Snow/Sand Ruins as well as a hidden town which allowed an deeper explanation of the game's backstory.

* The Seraphic Gate in all three ''VideoGame/ValkyrieProfile'' games. ''VideoGame/ValkyrieProfile2Silmeria'' and ''[[VideoGame/ValkyrieProfileCovenantOfThePlume Covenant]]'' scales up the difficulty every time you beat it, and all require them to be beaten at least 10 times to get the InfinityPlusOneSword, the latter two being far harder due to reasons stated above.
* The ''VideoGame/StarOcean'' games all have at least one BonusDungeon. The Seven Star Ruins in the [[VideoGame/StarOcean1 first game]], Cave of Trials in the [[VideoGame/StarOceanTheSecondStory second]], as well as its GaidenGame, and Maze of Tribulations in the [[VideoGame/StarOceanTillTheEndOfTime third]], which jacked up the pot by adding Sphere 211, another 100-level dungeon, and the Urssa Cave Temple, a more puzzle-oriented Bonus Dungeon. The [[VideoGame/StarOceanTheLastHope fourth game]] brought back the Seven Star Ruins and added the Wandering Dungeon. Many of these dungeons share the same background music (slightly remixed). ''VideoGame/StarOceanIntegrityAndFaithlessness'' has a large post-game dungeon called Maze of Tribulations, full of many {{superboss}}es and ending with the game's superboss, Gabriel Celeste. Also, when you complete it, you can challenge it again at increased difficulty two more times. (If you want HundredPercentCompletion, you will have to do this, as the powered-up versions of Gabriel Celeste have their own entries in the enemy database.)
* Yet another 100 floor dungeon exists in ''VideoGame/BeyondOasis''. There are prizes every 10 levels, and if you can make it all the way to the bottom without having to turn back to restock on supplies, your ultimate prize is an indestructible[[note]]most weapons break after limited uses, with the exception of your default dagger and a handful of well-hidden weapons[[/note]] [[InfinityPlusOneSword Omega]] [[FlamingSword Sword]].
* Mull's Dungeon in ''VideoGame/AtelierIris'' is only accessible after beating the game and contains a {{Superboss}} stronger than the final boss.
* The Chrysler Building in ''VideoGame/ParasiteEve''.

* ''VideoGame/Persona2'':
** ''Innocent Sin'':
*** The Abandoned Factory, where enemies from previous dungeons can be fought again. Different areas unlock depending on how far you're in the game, and several sidequests take place there, like the hunt for the legendary weapons.
*** The [[UpdatedRerelease PSP remake]] adds the Climax Theater, which features warped versions of [[VideoGame/Persona1 St. Hermilin High School]] and [[VideoGame/ShinMegamiTenseiIf Karukozaka High School]] as dungeons.
** ''Eternal Punishment'' has several.
*** The equivalent of the Abandoned Factory is Kasugayama High School and the bomb shelter underneath, which was a storyline dungeon in ''Innocent Sin''.
*** Later in the game, the Giga Macho music store and Mu Continent (both of which were also storyline dungeons in IS) open up when you spread a rumor about rare demons lurking there.
*** Finally there is the he EX Dungeon, available via NewGamePlus.
*** The PSP remake of the game adds Kadasu Mandala in the list, as part of ''Tatsuya's Scenario'', but only if you take Nanjo's route.
* Monad block in ''VideoGame/Persona3''. The game's ultimate boss can be fought on the final floor. Meanwhile, ''Persona 3 Portable'' has the Vision Quest, hosted by [[spoiler:Margaret, from ''VideoGame/Persona4'']] in the Desert Of Doors from FES. While not a dungeon in the same sense as Monad, it does feature superboss versions of all the Full Moon Shadows as well as hidden boss that some are claiming is harder than [[spoiler:Elizabeth/Theodore]]. Yes, you get to fight [[spoiler:Margaret. And she isn't going to cut you ''any'' slack.]]
* ''VideoGame/Persona4'': In the Golden version, if you maxed out the Aeon social link before New Year's Eve, you can enter the Hollow Forest on February 13...and ''only'' on February 13. If you don't do it on that day, not only is it gone, it's RetGone.
* ''VideoGame/Persona5'': In the Royal version, if you maxed out the Councillor confidant, you gain access to the third semester and the final Palace, the [[spoiler:Laboratory of Sorrow]]. This also unlocks a new area in Mementos.

* Chapter 8 in ''VideoGame/DarkChronicle'', which comes after defeating the main villain. Long story short, you go through an extra dungeon and end up fighting a hidden boss.
* ''VideoGame/ShinMegamiTenseiIIINocturne'' has both the Labyrinth of Amala and the Bandou Shrine. Completing the labyrinth gives you a sixth ending (and {{Superboss}}), and the shrine gives you the chance to acquire the [[InfinityPlusOneSword secret 25th Magatama]].
* Crossbone Isle of from ''VideoGame/GoldenSun1''. Not as difficult as a good deal of the examples listed already, but still can be a challenge. ''VideoGame/GoldenSunTheLostAge'' has Treasure Isle, Yampi Desert Cave, Islet Cave, and Anemos Sanctum, all of which have their own superbosses (which do not necessarily have to be beaten before taking on the Anemos Sanctum, but you might as well since you have to progress at least part of the way through each to get the Djinn inside before you can unlock it).
* ''VideoGame/{{Grandia}}'':
** The original ''VideoGame/Grandia1'' also contained no less than three bonus dungeon; the Castle of Dreams, the Soldiers Grave, and the Tower of Temptation, with the former two being available only for a limited time, and the latter being available to near the end of the game but nigh impossible to actually find. All of them have significantly ramped-up enemy difficulty (but absolutely abysmal experience payout), and all of them contain some of the most useful equipment for that point of the game.
** ''VideoGame/GrandiaII'' has the Raul Hills labyrinth, which hide the best defensive/recovery mana egg in the game.
** ''VideoGame/GrandiaXtreme's'' Vortex Corridor.

* Some ''VideoGame/DragonQuest'' games have added bonus opportunities as well, in each main series game starting with V and each remake starting with III.
** ''VideoGame/DragonQuestVI'' allowed you to defeat the equivalent of ''Satan'', upon which he beats up the normal final boss for you.
** ''VideoGame/DragonQuestVII'' features a BonusDungeon where you fight God. Literally. A second bonus dungeon features an easier bonus battle with the four elemental spirits seen earlier in the game, after which you get the chance to [[spoiler:invite God to live in your immigrant town]].
** ''VideoGame/DragonQuestVIII's'' BonusDungeon gives us the Hero's backstory, and a boss with several progressively different forms requiring different tactics to defeat- and his final form is styled to resemble [[spoiler:the final boss from the original ''VideoGame/DragonQuestI'', especially during his "psyche up" pose.]]
** The PSX/DS remake of ''VideoGame/DragonQuestIV'' includes a bonus dungeon which expands on the story, even allowing you to [[spoiler:redeem the [[ManBehindTheMan (apparent)]] BigBad, and the former final boss!]]
** The SNES/SFC remake of ''VideoGame/DragonQuestIII'' includes a new bonus dungeon which also adds a small piece to the story, enabling the hero to [[spoiler:revive his dead father as a wish granted by a [[Franchise/DragonBall Shenlong]]-like dragon... and part of the bonus dungeon itself is a sky castle the game calls "Zenithia" according to translations, suggesting a connection to Dragon Quest IV]]. The GBC version takes it a step further with an additional, story-less dungeon and boss to fight after that one... ''if'' the player can collect every single randomly-dropped Monster Medal in the game.
** ''VideoGame/DragonQuestV'': Estark's Labyrinth is unlocked after beating the main game. Estark, one of main enemies of ''VideoGame/DragonQuestIV'', lies at the end, with the difficulty significantly ramped up. Beating him unlocks the last [[MiniGame T'n'T board]] and beating ''that'' nets you the last two recruitable mons, who at this point are just for bragging rights. The real challenge is beating the {{Superboss}} in under fifteen rounds, which earns the final Knick Knack for your museum. Estark's Labyrinth was the first postgame bonus dungeon in the series.
** ''VideoGame/DragonQuestIX'' has a series of bonus story events, bosses, a few BonusDungeon areas (and several more randomly generated ones), and other content that can only be accessed after the main game "ends", including battling (and ''leveling up''!) the final bosses (and a few [[DiscOneFinalBoss less-than-final bosses]]) from the previous 8 games, but it really blurs the line since over half the playtime can be spent on postgame bonus content.
* In ''VideoGame/BaldursGate'', both the Ulcaster Ruins and Firewine Bridge are also completely optional. They are nowhere near as complex or deadly as Durlag's Tower though.
* ''VideoGame/BaldursGateTalesOfTheSwordCoast'' contains Durlag's Tower, a looming castle crammed full of thoroughly unpleasant enemies - and [[LudicrousGibs very large traps]].
* ''VideoGame/BaldursGateIIThroneOfBhaal'' has Watcher's Keep, a five-story dungeon (plus one extra for the boss fight) featuring some of the most complex puzzles and challenging fights in the game, eventually climaxing in a fight with [[spoiler:Demogorgon]], who is not only, as a good {{Superboss}} should be, the most poweful enemy in the game, but [[spoiler:the most powerful being in the entire [[TabletopGame/ForgottenRealms setting]]!]]
* The UpdatedRerelease of ''VideoGame/ChronoTrigger'' adds Dimensional Vortexes unlocked after the final boss, as well as [[ThatOneSidequest the Lost Sanctum]]. Even the original SNES version of the game has the Black Omen, an optional dungeon (although necessary to access NewGamePlus) that can, through the magic of TimeTravel, be cleared three times for maximum loot.
* ''[[Franchise/DotHack .hack]]'' gives us the Bonus Dungeons after the end of every game. In ''[[VideoGame/DotHackGU G.U.]]'''' one of those is called the [[NamesToRunAwayFromReallyFast Forest of Pain]]. How utterly appropriate.
* A third of ''VideoGame/{{Xenosaga}} 2'' is side-quests and another third Bonus Dungeons.

* ''VideoGame/ShirenTheWanderer'' has a bunch of extra dungeons you can take on after beating the main game, including the Kitchen God Dungeon (a special dungeon where you start with Bufu's Cleaver, a weapon that can turn enemies you kill with it into meat), the Cave Behind the Scroll (a possibly shorter dungeon where you start with a Trap Armband, which enables you to pick up and place traps and use them against enemies, as well as gain experience for killing them with traps), Fay's Final Puzzle (a 99-floor marathon where even herbs and scrolls that you find will be unidentified), the Tainted Path (''another'' 99-floor dungeon, with very strong monsters and a boss at the end), the Ravine of the Dead (a 50-floor frolick with tougher monsters, ''fake stairs'', and lots of Monster Houses), and the Ceremonial Cave (a 30-floor labyrinth with tough monsters and another boss). The first three of these dungeons don't allow you to bring any items or money, and you can't bring companions into Fay's Final Puzzle.
* The "Another Goddess" quest in ''VideoGame/HalfMinuteHero'', aside from being very long for the game's scope (most levels last about 30 seconds, while this one will take a good five minutes), harkens to another Marvelous Entertainment-created RPG: ''VideoGame/ValhallaKnights'' (the title even changes to reflect this). It's accessible during normal play, but because of the major change in style, the Time Goddess urges you to walk past it, on to the next quest. In order to actually play it, you have to defeat 108 bosses first. Harsh.
* There's six of the things in ''VideoGame/LastScenario'', seven if you count the one that's really just a sequence of four bosses. Luckily, all of them give you some ''very'' nice rewards.
* ''VideoGame/BlueDragon'' has the [[ExpansionPack downloadable]] Shuffle Dungeon, which gives you several new items to collect and some new monsters to fight.
* ''VideoGame/{{Torchlight}}'' has the Shadow Vault, known in FanSpeak as the Infinite Dungeon. ''VideoGame/TorchlightII'' has a dozen or more, ranging from level 45-105 and accessible through maps purchased from a special merchant after beating the main game.
* The ''VideoGame/MegaManBattleNetwork'' series is known for its expansive bonus dungeons, taking the form of huge mazes with doors that must be unlocked by completing some objective elsewhere in the game. [=BN2=] had [[spoiler: [[TheManBehindTheMan WWW Area]]]], 3 had [[ExactlyWhatItSaysOnTheTin Secret Area]], 4 had [[BrutalBonusLevel Murkland]], 5 had [[StormingTheCastle Nebula Area]], and 6 had the Graveyard, a SuperMode BossRush.
* In ''VideoGame/MuramasaTheDemonBlade'', there are several dead end paths that serve this purpose. When you beat the game once with both characters, all boss dungeons are available, turning them into this. Finally, the enemy lairs are bonus dungeons, including the aptly named level 92 Enemy Lair "Total Pandemonium/Night of Absolute Chaos." You have to fight through multiple waves of almost every type of enemy in the game. This includes some of the bosses [[spoiler:as well as clones of the player characters]].
* An early example in ''VideoGame/SwordOfVermilion''. Unlike all other dungeons in the game, nobody ever asks you to visit, or even mentions the existence of the dungeon where the [[InfinityPlusOneSword Death Sword]] is found.
* ''VideoGame/PhantasyStarIV'' had a couple of optional dungeons that contained some nice loot, and in one case a ContinuityNod to the previous installment.
* The Server Room in ''VideoGame/{{Opoona}}''. It opens up about midway through the game, but actually ''challenging'' it at such a point is not especially advisable. In addition to containing {{Mooks}} that are extremely fast, can heal themselves, and prevent you from using your Force (magic), the battle stages are full of bombs, which prevent you from using just about any hit-all abilities lest they explode. (And if they do so, they'll knock off about 100 HP--about three or four is enough for a TotalPartyKill.) And if ''that'' doesn't kill you, the room is also home to Salamanders, one of the game's most brutal BossInMookClothing monsters. However, you can leave at any time to save and heal without losing your progress.
* The ''VideoGame/FalloutNewVegas'' DLC ''Lonesome Road'' adds the Long 15 and Dry Wells maps, which are unlocked by launching nuclear missiles at NCR and Legion territory, respectively.
** Also, the Courier's Mile, an irradiated crater created by the missile launched from Ashton that is home to Irradiated Deathclaws and Irradiated Marked Men, the latter of which regenerate HP from the radiation, as well as two of the warheads required for the Warhead Hunter achievement.
** The main game has Deathclaw Promontory, home to the highest concentration of deathclaws in the game, as well as a suit of T-51b armor, a Multiplas rifle, and a tri-beam laser rifle. Also in the promontory is a suit of Enclave armor lacking a helmet, the latter of which can be found in Silverpeak Mine, guarded by the [[{{Superboss}} Legendary Cazador]]
** There's also Dead Wind Cavern, at the end of which is another {{Superboss}}, the Legendary Deathclaw, guarding the unique grenade machine gun [[ICallItVera named Mercy]].
** Some of the optional non-story dungeons in ''VideoGame/Fallout3'' may count, such as Deathclaw Sanctuary, the National Guard Depot, Fort Bannister, which also houses a {{Superboss}}, and the Dunwich Building.
* ''VideoGame/{{Wasteland}}'', the original Post-Apocalyptic RPG, had this in the form of [[ExactlyWhatItSaysOnTheTin Finster's Head]]. A one-man-solo "dungeon" ([[spoiler:VR sim, actually]]) in a party-oriented game that comes right after what passes for the game's WhamEpisode can catch you by surprise with its (entirely optional) {{Superboss}} that yields the largest XP boon in the whole game (DOUBLE that if you kill him in melee) and an inventive puzzle maze.
* ''VideoGame/KingdomOfLoathing'' has the Sea, which unlocks after you beat the game's BigBad, the Naughty Sorceress. It's full of tough monsters, exploring it initially requires you to wear an accessory that gives you a serious penalty to item drops and initiative, you can only take familiars that can breathe underwater with you, and unless you have a specific effect gained only by consuming certain items found in the Sea itself, it costs two adventures to explore a zone once. There's also the Clan Dungeons (Hobopolis, the Slime Tube, Dreadsylvania, and the Haunted Sorority House), which are intended for high-end players and full of tough monsters; and Fernswarthy's Basement, which is full of increasingly difficult challenges, but offers big stat bonuses every five levels, and powerful consumables that appear every 100 levels.
* ''VideoGame/FallenLondon'' has the Cave of the Nadir which requires a lengthy process to unlock: you need to first complete two opportunity card-based stories, then do a time-consuming expedition to find the Cave's entrance with a rare item that [[ArtifactOfDoom drains your attributes if you hold on to it for too long]], and finally pay a huge amount of money or find five of the aforementioned ArtifactOfDoom to actually open the Cave. After all that, your reward is the ability to explore a place that gives you opportunities to acquire valuable, hard-to-get items but [[LevelDrain erodes your attributes]] the longer you stay in there with a description of [[NightmareFuel your skull bones trying to grow over your eyes]] if you stay too long. Essentially, it trades the typical "slay extremely tough opponents!" bonus dungeon set-up for a "get valuable items dirt-cheap...if you're willing to weaken yourself!" set-up.
* ''VideoGame/EtrianOdyssey'' series has one BonusDungeon in each of the games, accessible only after you beat the FinalBoss. And each dungeon have a TrueFinalBoss also.
** ''VideoGame/EtrianOdysseyI'': Claret Hollows. A stratum with suspiciously organic features located within the deepest insides of the Yggdrasil Labyrinth, even below [[spoiler:the ruins of Lost Shinjuku]]. It has a brutal combination of hazards (such as teleporters that make navigation difficult and toxic puddles that are harmful upon contact) and powerful enemies, and hosts the Primevil (Yggdrasil Core) at the very end.
** ''VideoGame/EtrianOdysseyIIHeroesOfLagaard'': Forbidden Wood is a lush, seemingly-paradisial forest located far above the highest floors of Heavenly Keep. It's filled to the brim with dangerous monsters, and navigating across is is a big challenge on its own due to the high number of harmful ground areas, disorienting teleporters, and fog that reduces visibility. The boss is Ur Child, the ultimate creation of the Overlord and one of the strongest living beings in existence.
** ''VideoGame/EtrianOdysseyIIITheDrownedCity'': The Cyclopean Haunt is an eerie, seemingly-organic stratum whose walls appear to be made of flesh and tentacles, and features all sorts of vicious monsters and hazards (such as slippery slime that makes navigation difficult due to acting like FrictionlessIce, floor tiles that break upon being stepped on and take characters to a lower floor, and parts of the map that cannot be drawn or marked in any way). It is watched over by the almighty Abyssal God.
** ''VideoGame/EtrianOdysseyIVLegendsOfTheTitan'': The Hall of Darkness is an AbandonedLaboratory where Imperials used to work on a living failsafe should the Yggdrasil reach terminal corruption, only for that failsafe to end up killing everybody within and turn the whole place into a ghost building where all walls are stained in blood. In addition to hosting exceptionally strong enemies, it also has WrapAround corridors, toxic puddles, a huge warp maze, ice walls and ice floors that can be melted and later restored ([[TogglingSetpiecePuzzle which has to be done from time to time for a successful navigation]]), a room with a strong stench of miasma, and in the end the aforementioned failsafe: The Insatiable Pupa (which can grow to become the Warped Savior).
** ''VideoGame/EtrianOdysseyVBeyondTheMyth'': The Empyreal Bridge is an otherworldly labyrinth that goes well beyond not only Yggdrasil, but also the atmosphere of the planet, thus being a SpaceZone. Deceased planets can be seen from afar, and the stratum is home to vicious extraterrestrial creatures as well as hazards like toxic puddles, color-coded teleporters, and a layout and design that violates many laws of physics. Awaiting at the end is the Star Devourer, which is currently sealed and left in that state unless the player's characters wish to unseal it and start [[TrueFinalBoss the battle of their lives...]]
** ''VideoGame/EtrianOdysseyNexus'': The Abyssal Shrine (not the same one from ''Etrian Odyssey III'') has a layout and architecture reminiscent of the cardinal Shrines built all over Lemuria, and to a lesser extent the shrine built inside Yggdrasil Labyrinth, but the similarities end there. It features the most sordid fights against enemies (and have a much higher frequency rate than the RandomEncounters from all previous strata), as well as mind-bending {{Block Puzzle}}s that have to be solved for a successful navigation. It is here where the once-peaceful Abyssal Princess lies.
* ''VideoGame/EiyuuSenkiTheWorldConquest'' has Shambhala on its True End route and is considered the final challenge of the game due to it being 10 battles in a row of increasing difficulty and characters used in one battle cannot join any of the others.
* ''Avantasia: The Game'' has Via Inocencia, which is accessible only if you refuse to help any snakes during the main game.
* ''VideoGame/UncommonTime'' has two. After visiting the titular [[VisionQuest Uncommon Time]] in the main story, other gates to the dimension will activate -- once in the temple where Aubrey was hibernating, and after that, Arietta's grave. The former explores Aubrey's backstory, and the latter elaborates on Arietta's life during the time of the first World Tuning. Defeating the TrueFinalBoss after clearing both will net you the GoldenEnding.
* ''VideoGame/JimmyAndThePulsatingMass'' has multiple optional dungeons, called Nightmare Zones, and as one may get from the name, they are [[SurprisinglyCreepyMoment strikingly different in tone compared to the rest of the game]], featuring creepy environments and imagery, (usually) creepily looking enemies, and contain powerful creepy {{Optional Boss}}es in the end, who are much more difficult when compared to all other enemies faced prior.
** The first accessible Nightmare Zone is located in the Wilted Lands, [[spoiler:accessed by moving Punch Tanaka's pile of crashed motocycles using the Low-Level Goon form]]. It contains a creepy, claustrophobic environment that shifts to trap you inside and features creepy, hand-like rock formations. At the end lies [[SnakesAreSinister Slither]], an eyeless python who is even more difficult than the first boss.
** The second Nightmare Zone is located within Fermata Forest, [[spoiler:accessed by falling through the frozen lake by {{Ground Pound}}ing it in the Grumble Bear form]]. Described as "a dream within a dream", it's a very open hollow frozen wasteland, themed after dreams and fears of never being able to wake up again, with Sleepwalkers, the resident enemies, resembling sleep paralysis demons. At the end lies a castle, where Jimmy can end up being trapped permanently unless he directly enters the staircase hallway when clocks are ticking, and once he does, he is greeted by Ebeezil, the Emperor of Dreams, who is said to destroy the world should he ever fall asleep.
** The third Nightmare Zone is Turnbuckle's Mansion located in the Whispering Valley, [[spoiler:accessed by growing a vine from the fertile patch in the Happy Little Sunflower form to climb up into the mansion]]. It is a huge HauntedHouse where the gameplay shifts into the AdventureGame-esque exploration and item hunt. As you progress further through the mansion, a CreepyDoll will appear to play a game of hide-and-seek, constantly jumpscaring you as you progress, and eventually, the LivingToys of the mansion will come to attack you unless you satisfy the aforementioned CreepyDoll. At the end of the mansion, Turnbuckle himself, one of Jimmy's long-forgotten toys, will appear to attack him.
** Late in the game, the player can access a mountain at the Homeflower, where the formerly innocent crow used to fly around until it curled up in a ball, painfully undulating. The mountain features lots of acrophobic imagery, with the player constantly required to climb up, only to fall down on various collapsing bridges, with the enemies being zombified birds and bats, as well as Pud, a giant creepy cube-headed humanoid with NightmareFace. On the top of the mountain, the player faces [[CreepyCrows Grimclaw]], the crow fully mutated by the Pulsating Mass into a monstrosity with the worms inhabiting its body.
** After completing Cordelia Mouse's quest, the player will be informed by her family that she went missing. Under the Unbreakable Bridge, in the Mr. Cat's hideout, a closet will open, allowing the player to enter his dungeon, resembling a hollow gray mansion inhabited by hostile {{Living Shadow}}s. Halfway through the dungeon, the player will end up in the fake version of Smile, and after passing through the place, the player will end up in the cavern full of creepy eyes. At the end of the dungeon, the player confronts [[CatsAreMean Mr. Cat]], revealed to be a shadowy feline monstrosity, [[spoiler:and after defeating him, it's revealed that he murdered Coldelia Mouse in the cold blood.]]
** Another Nightmare Zone is accessible in the Legato Castle [[spoiler:by using 50's Style Vampire to enter the mirror in the castle's attic]]. It is told to serve as the prison to the former Queen of Legato and resembles the twisted form of ''Literature/AlicesAdventuresInWonderland'', with the enemies being figures based on the playing cards (such as Jack of Clubs, Queen of Hearts, the Joker, etc.), the recurring [=NPCs=] being a caterpillar playing riddles with Jimmy and the disembodied White Rabbit heads set on pikes, and the gruesome imagery of flayed skin and torture instruments being seen late in the dungeon. At the end, Jimmy meets the Mad Queen, who turned herself into a huge skeletal monstrosity and desires to flay Jimmy alive under the belief that she will be able to "cure" him.
** The second Nightmare Zone of the Legato Castle is accessible in Mr. Marvelous's home, [[spoiler:by opening the middle toy box when Helga is not in the party]]. It resembles the castle hallways full of chests, most of whom are [[ChestMonster Mimics]], and some either inflict negative effects on the player's next battle or increase the amount of money the player will get at the end of the dungeon. In the end, the player meets the Golden King, a golden LivingStatue standing among the piles of treasure, which can be stolen during the battle. However, the more treasure the player will steal, the more dangerous the Golden King will become. After beating the Golden King, the player will get the amount of money depending on how much treasure they stole from the boss, with the amount increased by how many rubies the player has collected at the dungeon.
** On Secret Meridian, [[spoiler:behind the Legs of Ancient Giant]], the player can access the Asymmetrical Cavern, a chaotic cave full of random patterns of numbers, with the music being the cacophony of voices yelling out random numbers interjecting with chaotic bass-line, and the enemies being the twisted geometrical figures or puzzles. The farther the player progresses, the more corrupted the cave will become, eventually resulting in the player being teleported at random, complete with the fakeout teleportation into the Path of Enlightenment, which is then followed by the reveal that they are still in the cave. At the end of the cave lie [[AnthropomorphicTypography Imaginary Numbers]], a bizarre, chaotic mess of symbols whose entire battle is a LuckBasedMission due to its random nature.
** In the cave under the Giant Garden, [[spoiler:behind the cobweb that can be burned by the Rotting Jack O'Lantern form]], the player can access another Nightmare Zone, themed around the darkness. The place is very dark, and the enemies here are various kinds of [[SpidersAreScary spiders]], obscured by the darkness until they reveal themselves. At the end of the dungeon, the player faces the Whisper Weaver, a creepy GiantSpider with the NightmareFace.
** Once Jimmy has 100,000 dollars on his [[InGameBankingServices bank account]], he can be invited for the luncheon for the Platinum Club members at the Accelerated Dynamics building. After leaving the luncheon room, he can enter the elevator, going to the higher floors of the building, only for the lights to flicker and the elevator releasing Jimmy in the office room, with the endless seas of cubicles. Despite being very mundane in appearance, with the enemies being the regular office people (along with [[TheLastOfTheseIsNotLikeTheOthers killing machines]]), it still maintains the creepy feel based on the [[SoulSuckingRetailJob disturbing monotone office working conditions]], with the background music consisting of nothing but office noises made into unsetting music track, the worker corpses hanging outside the windows, and one storage room with flickering lights occasionally flashing to replace the archive boxes with corpses and dismembered body parts. The boss of the location is [[spoiler:Mr. Grouse, formerly a friendly banker turned into a CorruptCorporateExecutive willing to murder a child just to keep his arms dealing practices a secret.]]
** Once Jimmy gets access to the spaceship, he can visit the Information Isle, home to the Information Guy. [[spoiler:Or rather, the Information Guys, as he's not the individual, but the entire species, with the zombified remains of the Information Guys killed all over the course of the game infesting the isle. At the end of the dungeon, the player faces a totem that reanimates the Information Guys' corpses.]]
** Once the player reunites all the missing monks of the Sacred Lantern, a Temple of the Inward-Looking Eye becomes accessible, and by using [[spoiler:the 50's Style Vampire form on the mirror]], the player can explore the rest of the temple. It is revealed to be the TempleOfDoom, with several areas being flooded, and the temple being inhabited by the marine life and Lovecraftian creature-cultists desiring to bring the apocalypse. At the end, the player faces the Black Prophet, leader of the ApocalypseCult using the DoomsdayClock to try to bring the end of the world, making him a TimeLimitBoss.
* ''VideoGame/AtelierSophieTheAlchemistOfTheMysteriousBook:'' After beating the final boss, you can download the additional map "Hidden Archive," which contains higher quality materials to gather, and tougher enemies to guard them. (Tormented Beast says hello!).
* ''VideoGame/BoxxyQuestTheGatheringStorm'' has two - the Deep Web and the Sky Abyss. The first is a [[MarathonLevel long]], confusing, and ''[[NightmareFuel terrifying]]'' labyrinth that can be accessed by gathering a set of keys held by seven specific [=NPCs=]. The second is unlocked in the epilogue by completing all of the Inbox missions, and leads to the game’s GoldenEnding.
* ''VideoGame/PiratesOfTheCaribbeanOnline'':
** The Cave of Lost Souls on Raven's Cove. It's totally optional, there's no quests that require visiting it, but it contains the toughest [[GhostPirate Ghost enemies]] in the game, including [[{{Superboss}} Foulberto Smasho]].
** The remake, ''The Legend of Pirates Online'', introduces Forsaken Shallows. It's below Isla Tormenta's Cursed Caverns, has five new bosses lying in wait, and holds the highest-level enemies in the game. It's also the only place where you can get [[InfinityPlusOneSword certain Legendary Cursed Blades]]. However, any quests that require fighting Davy Jones' minions can also be attained in the aforementioned (and slightly easier) Cursed Caverns, meaning you never have to step inside here unless you're looking for the strongest swords in the game.
* ''Monster Girl Quest: Paradox'' has the Labyrinth of Chaos, available after clearing the main game. It has two different sections, the Trials of Chaos and the Labyrinth of Chaos (yes, it has the same name as the area as a whole). The Trials of Chaos are ten floors in length, with a boss on the tenth floor, and are further divided into eight types that each have a different theme, enemies and rewards (e.g. the Eternal Forest consists of forest maps, is inhabited by forest enemies and contains light armour). The Labyrinth of Chaos has an infinite number of floors, with a boss every ten floors and an optional superboss every hundred floors. Also, both the Trials and the Labyrinth have different gameplay from the main game: enemies are PreexistingEncounters instead of RandomEncounters, you gain Rare Points as you progress, you get more valuable treasures based on your number of Rare Points, and you can upgrade equipment by applying Gems to it or merging two pieces of equipment.
* In ''Videogame/YakuzaLikeADragon'', after beating the game the [[VeryDefinitelyFinalDungeon Millenium Tower]] becomes the "Final Millennium Tower" filled with even stronger enemies and retreads of previous bosses, including the final boss. At the top is a member of the [[{{Superboss}} Amon Clan]] waiting to challenge your party. In NewGamePlus it becomes the "True Final Millennium Tower", in which you effectively have to be at the ''level cap'' to even stand a chance.
* ''VideoGame/{{Omori}}'' has the Recycultist's HQ. The difficulty mainly manifests in [[spoiler:the dungeon operating under [[SurprisinglyRealisticOutcome real life rules]], drastically reducing chances to heal Heart and Juice]].
* ''VideoGame/MonsterHunterStories2WingsOfRuin'' has the Elder's Lair, a 9-floor dungeon unlocked after beating the main game. To advance through each floor you have to perform specific quests, such as breaking certain body parts on the monsters, or completing puzzle fights within a certain time limit. After completing that, you unlock the S. Elder's Lair, a repeat of the Elder's Lair but with [[BrutalBonusLevel MUCH tougher monsters]]. At the bottom of both lies the game's {{Superboss}}: [[spoiler:the Fatalis, reprising its role from the [[VideoGame/MonsterHunterStories first game.]]]]
* ''VideoGame/EpicBattleFantasy'' series:
** ''VideoGame/EpicBattleFantasy3'' has special rooms accessed by having enough achievements. The one at Volcano Peak contains enemies stronger than the final boss.
** ''VideoGame/EpicBattleFantasy5'' has several bonus areas, many exclusive to the Steam version.
*** The Freezeflame Dungeon, Mineshaft Maze, Deathly Hallows, and Crystal Caverns are caves smaller than the main dungeons proper. Each of them has a stronger counterpart to a main story boss fought at the end, with the Crystal Caverns having an extra boss on top of that.
*** Version 2 updated Greenwood Library to have a short dungeon with unique enemies, culminating in a BossBonanza against four living sketches.
*** The Great Sea in Version 2 has both a NostalgiaLevel and an area where the team is restricted to one party member.
*** All versions of the game have five Glitch Areas making up one sidequest, and three small basement dungeons and the Forgotten Temple making up another.
*** The Temple of Trials is the game's BrutalBonusLevel, intended to be the hardest of the optional areas.

* ''VideoGame/MinecraftDungeons'': There are secret dungeons that can be accessed after you find a scroll that unlocks them in their parent dungeon. There are 5 of these in the base game, with each Island Realm [=DLC=] having only one, which are always found in their first mission. The Nether and End [=DLCs=] do not have these as the former has their scrolls placed out in the open on the main path (though they're still labelled as secret missions) while the latter doesn't have any secret missions.
** [[spoiler:The Secret Cow Level, being a reference to the one in ''VideoGame/DiabloII'', can be unlocked after completing the game on Default difficulty and collecting a rune that is hidden in every main mission in the base game]].

* In ''VideoGame/MinecraftDungeons'', there are unlockable extra dungeons, most of which can be accessed after you find a scroll that unlocks them in their parent dungeon. And then there's [[spoiler:the Secret Cow Level, referencing the one in ''VideoGame/DiabloII'', which can be unlocked after collecting hidden runes in every main level]].

** The Omega Ruins in ''VideoGame/FinalFantasyX''.

* ''VideoGame/YuGiOhReshefOfDestruction'' has the Hall of Eternity, where you can battle Yami Yugi, Yami Marik, Yami Bakura, Dark Joey/Jounouchi, Noah Kaiba, Pegasus, Shadi, and Paradox.

** ''VideoGame/TheLegendOfZeldaLinksAwakening [[UpdatedRerelease DX]]'' has the Color Dungeon, which is only accessible by playing the game on a Game Boy Color. It includes color-based puzzles, such as colored switches and enemies that are only distinguishable by their tunics having to be beat in a certain order. For winning, you get either a Red or Blue Tunic, which puts you permanently under the effect of a Piece of Power (increased speed and attacks send enemies flying and do double damage) or a Guardian Acorn (double defense), respectively.

* ''VideoGame/JimmyAndThePulsatingMass'' has multiple optional dungeons, called Nightmare Zones, and as one may get from the name, they are [[SurpriseCreepy strikingly different in tone compared to the rest of the game]], featuring creepy environments and imagery, (usually) creepily looking enemies, and contain powerful creepy {{Optional Boss}}es in the end, who are much more difficult when compared to all other enemies faced prior.

** ''VideoGame/FinalFantasyLegendII'' (''Final Fantasy Legend II'' in North America) has the aptly-named Nasty Dungeon with single-tile hallways that span multiple screens and lead to dead ends and monster encounters the party cannot run from. Naturally the strongest weapons and equipment in the game are found here.

* The ''VideoGame/StarOcean'' games all have at least one BonusDungeon. The Seven Star Ruins in the [[VideoGame/StarOcean1 first game]], Cave of Trials in the [[VideoGame/StarOceanTheSecondStory second]], as well as its GaidenGame, and Maze of Tribulations in the [[VideoGame/StarOceanTillTheEndOfTime third]], which jacked up the pot by adding Sphere 211, another 100-level dungeon, and the Urssa Cave Temple, a more puzzle-oriented Bonus Dungeon. The [[VideoGame/StarOceanTheLastHope fourth game]] brought back the Seven Star Ruins and added the Wandering Dungeon. Many of these dungeons share the same background music (slightly remixed). ''VideoGame/StarOceanIntegrityAndFaithlessness'' has a large post-game dungeon called Maze of Tribulations, full of many {{Bonus Boss}}es and ending with the game's superboss, Gabriel Celeste. Also, when you complete it, you can challenge it again at increased difficulty two more times. (If you want HundredPercentCompletion, you will have to do this, as the powered-up versions of Gabriel Celeste have their own entries in the enemy database.)

* Monad block in ''VideoGame/Persona3''. The game's ultimate boss can be fought on the final floor. Meanwhile, ''Persona 3 Portable'' has the Vision Quest, hosted by [[spoiler:Margaret, from ''VideoGame/Persona4'']] in the Desert Of Doors from FES. While not a dungeon in the same sense as Monad, it does feature Bonus Boss versions of all the Full Moon Shadows as well as hidden boss that some are claiming is harder than [[spoiler:Elizabeth/Theodore]]. Yes, you get to fight [[spoiler:Margaret. And she isn't going to cut you ''any'' slack.]]

* Crossbone Isle of from ''VideoGame/GoldenSun1''. Not as difficult as a good deal of the examples listed already, but still can be a challenge. ''VideoGame/GoldenSunTheLostAge'' has Treasure Isle, Yampi Desert Cave, Islet Cave, and Anemos Sanctum, all of which have their own bonus bosses (which do not necessarily have to be beaten before taking on the Anemos Sanctum, but you might as well since you have to progress at least part of the way through each to get the Djinn inside before you can unlock it).

** The Battle Frontier in the various games are all single player[[note]]Although some Generation 4 games had very basic online stuff, and Black and White added a rather robust online component[[/note]] tournaments with various gimmicks, which also tend to be source of the better hold items, evolution trinkets, technical machines, etc. This means that if you are going for HundredPercentCompletion (or wish to be tournament viable) you will need to master these game modes. Unfortunately TheComputerIsACheatingBastard is in ''full'' and ''blatant'' effect.

* The ''VideoGame/MegaManBattleNetwork'' series is known for its expansive bonus dungeons, taking the form of huge mazes with doors that must be unlocked by completing some objective elsewhere in the game. [=BN2=] had [[spoiler: [[TheManBehindTheMan WWW Area]]]], 3 had [[ExactlyWhatItSaysOnTheTin Secret Area]], 4 had [[BonusLevelOfHell Murkland]], 5 had [[StormingTheCastle Nebula Area]], and 6 had the Graveyard, a SuperMode BossRush.

* The ''VideoGame/MegaManBattleNetwork'' series is known for its expansive bonus dungeons, taking the form of huge mazes with doors that must be unlocked by completing some objective elsewhere in the game. [=BN2=] had [[spoiler: [[ManBehindTheMan WWW Area]]]], 3 had [[ExactlyWhatItSaysOnTheTin Secret Area]], 4 had [[BonusLevelOfHell Murkland]], 5 had [[StormingTheCastle Nebula Area]], and 6 had the Graveyard, a SuperMode BossRush.

** ''VideoGame/TalesOfVesperia's'' Memory Dungeon. The graphics are blurry, [[RealIsBrown it's brown]], and all the sound effects sound far away, like you're hearing them on a camcorder recording the actual video game. In here, you fight the party's memories, and with that, every enemy they've faced in the game. This makes for some weird situations, like StoneWall WhiteMage vs. [[spoiler: BrainwashedAndCrazy WhiteMage]] and GrumpyOldMan vs. [[spoiler:the other half of his SplitPersonality.]] Strangely, for a game whose characters lampshade many things such as {{Crack Pairing}}s and DudeLooksLikeALady, this wasn't remarked about at all. The [=PS3=] UpdatedRerelease ups the ante with the Garden of Izayoi, an [[MarathonLevel incredibly long]] dungeon with the gimmick of progressing through the floors by way of actual combat; once you defeat a group of enemies, paths on the battlefield open up for you to traverse to another battlefield with more enemies, and you make your way through several floors of mazes. There are plenty of new {{Bonus Boss}}es, including a horrific "monster" called [[spoiler:the Spiral Draco, the King of the Entelexeia]], which appears to have taken the title of "most difficult boss in the ''VideoGame/TalesSeries''."

** ''VideoGame/TalesOfBerseria'' has The Heavenly Steppes (also called the EX Dungeon), which can be unlocked by reloading a save made after defeating the final boss. It features 6 different levels, each one harder than the previous. The level starts with one of a few random layouts including unique monsters (unique to the level, not to the layout type). Next is a layout that mimics an area from earlier in the game, including more of that level's monsters, chests, and a mission to complete several battles in a certain amount of time before the door is opened so they can proceed to the boss. There are some great equipment and abilities to be unlocked here, but the final boss gets stronger with each level of the area, and you must defeat the boss again in order to take any grade/potentites you've acquired into NewGamePlus

* The ''Franchise/KingdomHearts'' series, while known for its slew of hidden {{Bonus Boss}}es, occasionally features some of these:

* ''VideoGame/XenobladeChroniclesX'' has several optional caves and Ganglion outposts, but the most prominent two are the Ganglion Anthropolis and the Divine Roost. It's only available after starting the mission "Definian Downfall", which in turn requires the completion of a large amount of previous missions. It's rife with many powerful enemies whose level swing between 55 and 65, and is home to powerful opponents like Urdu (accompained by several Milsaadi followers), a Level 85 Ganglion Skell, Rexoskell and Blood Despair. The Divine Roost is only accessible via flying skells and has three powerful tyrants and quite a few over level 60 enemies including Telethia the Endbringer, the hardest boss in the game.

This is where the BonusBoss usually lives. Sometimes, the InfinityPlusOneSword will be waiting at the bottom.

** ''VideoGame/DonkeyKongCountryReturns'' and ''VideoGame/DonkeyKongCountryTropicalFreeze'' have the Golden Temple and Secret Seclusion respectively, both accessible only after completing the Temple levels in the regular worlds.
* ''VideoGame/DistortedTravesty'' has a number of unusually difficult bonus areas that open up along the way. However, the big one is the Spire of Forgotten Souls, a 100 floor TimedMission[[note]]although you get a time reset and full heal every 5 floors[[/note]] filled with some of the most devilish PlatformHell that the creator could come up with. The BonusBoss lurks at Floor 100, as well.

* ''VideoGame/CopyKitty'' features World 13, a bonus set of levels exclusive to Boki's campaign, featuring unique hell and heaven-based enemies in environments that sharply contrast the rest of the game. The Normal version has blood, bones, and a darker color palette with an EldritchAbomination at the end of a difficult series of levels with downright bizarre powers to copy. On Hard Mode, after [[DoubleUnlock completing a lengthy checklist of achievments]], the levels feature holy-themed enemies with more unique abilities and a truly spectacular BonusBoss.

** ''VideoGame/FinalFantasyIII'' had one of these ATTACHED to the VeryDefinitelyFinalDungeon, with a TON of BonusBoss characters, each guarding a specific class' InfinityPlusOneSword. Though it is mostly easier than the rest of the dungeon, and the game itself recommends to tackle it. There also several others throughout the game like the Sunken Cave and Bahamut's cave. The 3D remake also adds an optional "???" dungeon, in which the all-new superboss is fought.

** Fanatics' Tower in ''VideoGame/FinalFantasyVI'', as well as Ebot's Rock, the Ancient Castle, and many others, all available during the second half of the game. Also the Dragon's Den in ''VideoGame/FinalFantasyVI Advance'', which is much more hardcore than any of those, and has a ''MUCH'' harder BonusBoss. The Soul Shrine, also added in the GBA version, is something of a boss rush mode.

** ''VideoGame/LightningReturnsFinalFantasyXIII'' has the Ultimate Lair, only accessible if you've completed enough sidequests to unlock [[spoiler:the 14th day]]. Each floor is inhabited by a different [[BossInMookClothing Last One]], unless you've already driven the species to genocide, and a BonusBoss fight awaits on the final floor. The catch? The in-game clock continues ticking during battles, making the dungeon a TimedMission.

** ''VideoGame/PaperMarioTheThousandYearDoor'' contains a bonus level called the Pit of 100 Trials, consisting of 100 floors populated by increasingly tough enemies. Every tenth floor is a rest floor with a new badge/item and a pipe you can use to leave, but you have to clear the lot in one go to reach Bonetail, the BonusBoss that lives at the bottom.
** ''VideoGame/SuperPaperMario'' has not one but ''two'' Pits of 100 Trials, one for Flipside and one for Flopside. The former is reminiscent of that of the previous game, and home to Wracktail, an upgraded version of the first boss Fracktail. The Flopside Pit, on the other hand, is populated solely by "Dark" versions of the game's enemies that are far stronger than those found elsewhere. To make things even worse, you ''have to clear it twice'' before the final BonusBoss, [[MirrorBoss Shadoo]], will face you. Post-game you can also visit [[spoiler:Sammer's Kingdom for the complete Duel of 100. One hundred battles in a row, with no interruptions like in the main story. You do get to save after every 25 fights, at least, unlike the Pit of 100 Trials.]]

** The games have these, starting with Mewtwo's lair, the Cerulean Cave in ''VideoGame/PokemonRedAndBlue''. They are inaccessible until after you've beaten the game, and at the end lies a powerful legendary Pokemon for the player to catch, making it both a BonusBoss and an InfinityPlusOneSword. Generations II and III possess a different variant. After the bonus dungeon you encounter, rather than a high-level Pokémon, a trainer with ''six'' high-level Pokémon, often the highest in the game. In ''GSC'', this is [[spoiler:Red, the protagonist of the original games as well as the male choice of protagonist in their [[VideoGameRemake remakes]], ''[=FireRed=]''/''[=LeafGreen=]'', with a party including a level 80 ''Pikachu'' and 70+ versions of all three original starters, Snorlax... and Espeon, for some reason. ''HGSS'' replaces the Espeon with a Lapras. The whole match has continuous hail and all of their levels have been buffed up. ''Pikachu'' is level 88 now!]] In ''Emerald'', it's [[spoiler:Steven, the mandatory FinalBoss of the first two games of that generation, now cranked up to 11 as a BonusBoss. He has a similar team to the previous game (which was bad enough), but now they're all around level 80 rather than 50-60.]] Both fights are bragging rights only and give no real reward (although they are in fact repeatable, making them among the best spots to grind high-level Pokémon).

* Mull's Dungeon in ''VideoGame/AtelierIris'' is only accessible after beating the game and contains a BonusBoss stronger than the final boss.

* Pork City in ''VideoGame/TheWorldEndsWithYou''. You visit the first two floors as part of the main story, but the other 11 floors and the BonusBoss aren't unlocked until Another Day.

* ''VideoGame/ShinMegamiTenseiIIINocturne'' has both the Labyrinth of Amala and the Bandou Shrine. Completing the labyrinth gives you a sixth ending (and BonusBoss), and the shrine gives you the chance to acquire the [[InfinityPlusOneSword secret 25th Magatama]].

** ''VideoGame/DragonQuestV'': Estark's Labyrinth is unlocked after beating the main game. Estark, one of main enemies of ''VideoGame/DragonQuestIV'', lies at the end, with the difficulty significantly ramped up. Beating him unlocks the last [[MiniGame T'n'T board]] and beating ''that'' nets you the last two recruitable mons, who at this point are just for bragging rights. The real challenge is beating the BonusBoss in under fifteen rounds, which earns the final Knick Knack for your museum. Estark's Labyrinth was the first postgame bonus dungeon in the series.

* ''VideoGame/BaldursGateIIThroneOfBhaal'' has Watcher's Keep, a five-story dungeon (plus one extra for the boss fight) featuring some of the most complex puzzles and challenging fights in the game, eventually climaxing in a fight with [[spoiler:Demogorgon]], who is not only, as a good BonusBoss should be, the most poweful enemy in the game, but [[spoiler:the most powerful being in the entire [[TabletopGame/ForgottenRealms setting]]!]]

** The main game has Deathclaw Promontory, home to the highest concentration of deathclaws in the game, as well as a suit of T-51b armor, a Multiplas rifle, and a tri-beam laser rifle. Also in the promontory is a suit of Enclave armor lacking a helmet, the latter of which can be found in Silverpeak Mine, guarded by the [[BonusBoss Legendary Cazador]]
** There's also Dead Wind Cavern, at the end of which is another BonusBoss, the Legendary Deathclaw, guarding the unique grenade machine gun [[ICallItVera named Mercy]].
** Some of the optional non-story dungeons in ''VideoGame/Fallout3'' may count, such as Deathclaw Sanctuary, the National Guard Depot, Fort Bannister, which also houses a BonusBoss, and the Dunwich Building.
* ''VideoGame/{{Wasteland}}'', the original Post-Apocalyptic RPG, had this in the form of [[ExactlyWhatItSaysOnTheTin Finster's Head]]. A one-man-solo "dungeon" ([[spoiler:VR sim, actually]]) in a party-oriented game that comes right after what passes for the game's WhamEpisode can catch you by surprise with its (entirely optional) BonusBoss that yields the largest XP boon in the whole game (DOUBLE that if you kill him in melee) and an inventive puzzle maze.

** The Cave of Lost Souls on Raven's Cove. It's totally optional, there's no quests that require visiting it, but it contains the toughest [[GhostPirate Ghost enemies]] in the game, including [[BonusBoss Foulberto Smasho]].

* In ''Videogame/YakuzaLikeADragon'', after beating the game the [[VeryDefinitelyFinalDungeon Millenium Tower]] becomes the "Final Millennium Tower" filled with even stronger enemies and retreads of previous bosses, including the final boss. At the top is a member of the [[BonusBoss Amon Clan]] waiting to challenge your party. In NewGamePlus it becomes the "True Final Millennium Tower", in which you effectively have to be at the ''level cap'' to even stand a chance.

* ''VideoGame/MonsterHunterStories2WingsOfRuin'' has the Elder's Lair, a 9-floor dungeon unlocked after beating the main game. To advance through each floor you have to perform specific quests, such as breaking certain body parts on the monsters, or completing puzzle fights within a certain time limit. After completing that, you unlock the S. Elder's Lair, a repeat of the Elder's Lair but with [[BrutalBonusLevel MUCH tougher monsters]]. At the bottom of both lies the game's [[BonusBoss superboss]]: [[spoiler:the Fatalis, reprising its role from the [[VideoGame/MonsterHunterStories first game.]]]]

** The series, unusually for ShootEmUp games, has made a tradition out of this. Of all mainline games, only [[VideoGame/TouhouReiidenHighlyResponsiveToPrayers the first game]] (which isn't a shooter) and [[VideoGame/TouhouYumejikuuPhantasmagoriaOfDimDream the third game]] (which is a versus shooter) don't have any Extra Stages. Typically, the Extra Stage is unlocked after you've beaten all stages of the normal game without using any Continues (on Normal difficulty or higher for earlier games, later games allow for any difficulties). Storyline-wise, after defeating the FinalBoss of the current game and solving the incident, the heroines are once again faced with another, smaller incident that is related to the main incident. They then set off once again to meet the BonusBoss. Alice and Marisa's [[WrongGenreSavvy pretending the game is an RPG]] in ''VideoGame/TouhouChireidenSubterraneanAnimism'' leads to the page quote in that game's extra stage.

* The Hellgate from ''VideoGame/TacticsOgre'' was 100 levels deep, and interestingly actually tied into the plot, as the bottom level was where one of the [[BonusBoss villains]] in the game had retreated to. Beating him didn't change the main plot of the game, though. In order to get the ultimate "bragging" item in the game, one had to go through the Hellgate twice, as well as get 4 specific weapons from special encounters with recolored monsters.

** The Floating Catacombs in ''VideoGame/CastlevaniaSymphonyOfTheNight''. It's home to [[BonusBoss Galamoth]], [[{{Superboss}} the most powerful boss in the game]]; defeating him nets you the Gas Cloud relic, which makes your mist form harm enemies. The Floating Catacombs are completely optional, since there are no Vlad relics up there.

** The Floating Catacombs in ''VideoGame/CastlevaniaSymphonyOfTheNight''. It's home to [[BonusBoss Galamoth]], [[ThatOneBoss the most powerful non-Dracula boss in the game]]; defeating him nets you the Gas Cloud relic, which makes your mist form harm enemies. The Floating Catacombs are completely optional, since there are no Vlad relics up there.

* ''VideoGame/{{Okami}}'' features a particularly evil example. In different areas of the overworld there are three caves that are home to (slightly) upgraded versions of a previous giant demon spider boss. Defeating them earns a reward, but you can then return to the same cave later to find a demon gate eerily sitting there. Going through forces you to battle wave after wave of superpowered regular enemies. Even the lowliest of {{Mooks}} can waste you with a couple of hits in these battles (and you have to go through 10 of them to get the reward) and have HP that would make some of the late-game bosses jealous. These battles could be considered a refreshing change of pace compared to the general easiness of ''Okami'' if not for their sheer sadism. The most difficult cave has you face several bosses from the past in groups, usually two or three at a time. Including [[spoiler:Waka and two possessed Raos]].

** The Consecrated Snowfield is a fairly hidden away very late game area, teeming with very strong late game enemies like the Albinauric archers. Half of the area is also covered in a blizzard, obscuring vision and hiding these enemies. This area also gives access to the Mohgwyn Palace and to Miquella’s Haligtree. This area is only accessible by collecting two medallions - one in Liurnia in a fairly hidden away village.. and the other far later into the game in a tough as nails castle. You’ll have to get it by defeating a ridiculously hard boss in Commander Niall.
** The Mohgywn Palace is fairly small but absolutely full of tough enemies that abuse blood loss, a [[ScrappyMechanic very strong mechanic]] that shreds through your health when fully built up, and one of the game’s [[SuperBoss hardest bosses]], the Lord of Blood Mohg. Guess what he also abuses. This area can only be accessed through progressing through Varré’s quest line, or through finding a rather obscure portal in the Consecrated Slowfield.

*** The Cave of Ordeals, a gauntlet of monsters similar to the ones in ''The Wind Waker'', with monsters ranging from a single one of the weakest monsters in the game, to three of the strongest and fastest monsters at the same time. If you can reach the bottom, you'll find an inexhaustible supply of a potion that fills your health gauge and temporarily boosts your offensive capabilities, making you unstoppable in combat. Although if you ''can'' reach the bottom, you likely won't need that kind of advantage, even against the final boss. You can go back to it afterwards and find the [[UpToEleven the difficulty has increased]].

* ''VideoGame/FireEmblemGaiden'' has one in its remake, ''Echoes: Shadows of Valentia'', in the form of the [[RuinsForRuinsSake Thabes Labyrinth]], a ten-level dungeon unlocked in a special "Act 6" after beating the FinalBoss and accessing the clear save data. Story wise, the Labyrinth chronicles the story of an alchemist named Forneus [[spoiler:and the origins of the Fell Dragon Grima, the BigBad of ''VideoGame/FireEmblemAwakening'']]. Gameplay wise, it is extremely [[BrutalBonusLevel brutal]]. [[CheckpointStarvation The entire dungeon doesn't have a single save point]] (not counting {{Suspend Save}}s) and is filled to the brim with extremely beefed-up mooks. The boss of the dungeon, [[spoiler:Grima himself,]] is even accompanied by {{Elite Mook}}s that would otherwise spawn in extremely rare encounters. Not helping is the boss has an ArmorPiercingAttack and most enemies have more HP than the HP bar can display.

* Elden Ring has plenty of these:

** Miquella’s Haligtree probably fits this trope best. Only accessible through solving a puzzle in the aforementioned Consecrated Snowfield, and you’ll have to deal some nasty Black Knife Assassins and Albinauric Archers to do this. Once you’re there, you’ll be met with a rather beautiful town in a tree. That’s absolutely full of the toughest late game enemies. Much of the level takes place on tree branches where you have a very high chance of simply falling off. And even when you’re on safer ground, it’s hardly safe. Be prepared to deal with knights, battle mages, soldiers everywhere, Kindred of rot that now hit like a truck with their pest threads, bosses roaming around like Erdtree Avatars, pools of Scarlet Rot that you can’t run through, and (most sadistically) an Ulcerated Tree Spirit fought on a tiny platform to be able to finish Millicent’s questline. One (thankfully optional, but that hide ) section of the dungeons even has five of the infamous [[DemonicSpiders revenants]] in one passageway!! The end boss of the dungeon? None other than the hardest boss in all of Elden Ring, and arguably in ALL FROMSOFT GAMES, [[SuperBoss Malenia]], complete with two phases, scarlet rot attacks, lightning speed, hovering attacks, lifesteal.. and Waterfowl Dance.