History YMMV / DungeonCrawl

** The three [[GodOfGood Gods Of Good]] get a bit of this, due primarily to the EverythingTryingToKillYou nature of the game. A game played as a follower of one of the good gods (even Elyvilon, the supposedly pacifist god of healing) will see the player committing wholesale slaughter just as they would as a follower of a neutral or even evil god. This has led some players to question whether the good gods are really so good after all.
*** Made even worse in Elyvilon's case. Pacifying monsters makes them neutral not just to you but to other monsters, and they will attack other monsters that are in their way. Manipulating enemies into attacking each other is actually the most efficient way to "fight" as a follower of Elyvilon, as it not only helps you train your invocations, it also doesn't count as a kill on your part and so won't earn you penance if you do it while under Divine Protection. So a typical follower of the pacifist healer god goes around brainwashing everyone they see and tricking people into murdering their friends.

** Hell, which also qualifies as BonusLevelOfHell, as befits its name. To even enter you need to kill the archdemon Geryon, who almost qualifies as a ThatOneBoss thanks to his EnemySummoner nature. Once he's down you have your pick of four equally lethal regions: the iron city of Dis, the fiery Gehenna, the undead-filled Tartarus, and the icy Cocytus. Each region is filled with hordes of demons, including large numbers of tier 1 and tier 2 demons, and is guarded by a powerful unique archdemon down at the very bottom. While that's bad enough, what really qualifies Hell for ThatOneLevel status is ''the Mystical Force'', a vaguely explained... well, mystical force that regularly (every twenty turns or so) does some random bad thing to you. If you're lucky it'll only decide to confuse you (probably while you're standing right next to lava and/or in combat). If you're unlucky it'll decide to blast you with massive unresistable damage, stat drain you to death, or summon a tier 1 demon right next to you while you're trying to rest.
*** Followers of the god of order, Zin, will be granted (not infallible) protection against Hell's mystical force, which makes them among the most suited to taking on this level, but even they have to be very careful of the demons and other monsters here.
** The Tomb is considered to be the most hazardous of the game's many side areas. It's an undead-themed branch with an Egyptian flavor to it, meaning lots of traps and lots of mummies, most of which will spend their time either smiting you, spamming [[PercentDamageAttack Torment]], or [[EnemySummoner summoning demons]]. What makes it so deadly is the mummy death curse; whenever you kill a mummy, you get hit with some sort of magical backlash. For basic mummies, this just curses a random item in your inventory, but the more powerful ones can torment you, shave off chunks of your health with Pain spells, rot your flesh, drain your stats, or summon demons. In short, mummies can hurt you no matter what you do, and since there's lots of them, this adds up very quickly. If you try to brute-force the Tomb, '''you will die'''.
*** The Tomb was made more dangerous when all the stairs were made 1-directional. Prepare to be ambushed without a convenient escape should you visit.
** The endgame, after collecting the Orb of Zot and you're ascending back toward the surface. You'd expect an easy return since you've already cleared all the floors, right? Wrong! First, while holding the Orb of Zot your stealth is decreased drastically, which can be very damaging for certain characters. Add to that, teleportation takes a lot longer to take effect, and the duration of [[TheCorruption magical contamination]] is greatly extended. What's more, the game will constantly spawn new enemies to attack you, drawn from the Hell and Pandemonium lists. This includes Pandemonium Lords, which are the strongest non-unique enemies in the game and ordinarily only appear at a rate of one or less per floor in the demon plane of Pandemonium, but during the ascent you can fight multiples per floor, or even 2 or more at once.
*** In keeping with the apparently masochistic nature of Crawl players, one somewhat popular SelfImposedChallenge involves waiting until the ascent to clear the Tomb, thereby having to deal with all of the Tomb's normal hazards, as well as the massively powerful demons summoned by the Orb. (The challenge would also involve clearing the four regions of Hell, but once the Orb is picked up, all of the portals to Hell are sealed.)

*** Brimstone Fiends, Ice Fiends, and Shadow Fiends are all tier 1 demons most reviled for knowing (and loving to abuse) the spell Torment, which [[PercentDamageAttack cuts your current HP in half]] with every use and is unresistable for most characters. While all monsters who know Torment are bad, Fiends up the ante by adding other nasty attack spells plus summoning hordes of minions. Shadow Fiends are perhaps the worst since they have the spell Dispel Undead, which deals massive damage to undead characters, who incidentally are the only ones able to reliably resist Torment.

** Absolute Zero instakills whatever monster is closest to you. No resisting, no dodging, no blocking, they are ''dead''.
*** As of 0.27, Absolute Zero has been removed due to being too strong. Its effect was moved to a level 8 Air magic spell, which has a delay between the cast and the instakill.

*** Later on you'll also run into Unseen Horrors, which are just like bats except they actually have decent attack and HP. Oh yeah, ''and they're invisible.'' (See DemonicSpiders, above.)

* NightmareFuel: If you have a good imagination, there could be plenty. Using Animate skeleton on a fresh corpse is one such case ("Before your eyes, flesh is ripped from the corpse!"). Another one is when you make an enemy bleed with your sharp claws and they proceed to run around the dungeon [[HighPressureBlood painting it red]].

* FridgeBrilliance: If you kill the Royal Jelly, [[spoiler: Jiyva the Slime God dies, supposedly due to the Royal Jelly being its only intelligent follower... except that's not true. Jiyva has one more intelligent follower: Dissolution, the High Priest of Jiyva. So why doesn't Dissolution keep Jiyva alive too? ''Because Dissolution hates Jiyva.'' Dissolution was formerly the high priest of an ancient civilization that was destroyed by Jiyva, and he was forced to convert or die. He ''wants'' Jiyva to die for this, and as such will abandon the god if its other intelligent follower is defeated.]]

** Hydras, the bane of squishy stealth characters and evasion-based fighters. They spawn with anywhere between four and eight heads, and while their attacks aren't bad individually, they get one attack per head - meaning an eight-headed hydra will hit you ''eight times per turn'', which tends to add up fast. Now, you can chop off their heads with an edged weapon like an axe or a longsword...but unless it's a ''flaming'' edged weapon, the hydra will grow two heads in its place and heal a significant chunk of health. They're also resistant to poison, and have enough MR to reliably resist most hexes you can cast at this point of the game, making it hard to disable or weaken them. Thankfully, they don't have much in the way of resistances ''besides'' that, and their physical defenses are fairly lacking.

** Spiny frogs are the bane of many casters, with poison resistance to nullify Mephitic Cloud, surprisingly potent melee attacks, and fast movement speed.

** Maurice. A thief that'll haste himself, turn invisible, then sneak up to you and [[VideoGameStealing yoink your stuff]]. Losing your stuff is bad enough (though you will get it back if you can kill him) but depending on what he manages to get from you he can become extremely powerful. If he grabs a potion of healing he can be back to full health in a second. If he grabs a powerful enough wand then bend over and kiss your ass goodbye.
** Then there's Gastronok, a giant slug who became a mage after [[CannibalismSuperpower eating a wizard]]. Unlike most mage characters, Gastronok is surprisingly tough, having more HP than even equal-level melee threats like orc knights. He also has the [[BlowYouAway Airstike]] spell which deals a ton of damage and hits with 100% accuracy, plus it's smite-targeted, meaning it can hit you even if he doesn't have a clear line of fire to you. Add to that his ability to [[EnemySummoner summon swarms of rats]] on you. His one disadvantage is an inherently slow movement speed thanks to being a giant slug, but he can even overcome that by casting slow spells on the player and haste on himself.

** The Royal Jelly, boss of the Slime Pits and guardian of the Slimy Rune Of Zot. It's got an impressive amount of HP and hits like a mack truck, plus it has the same ability to corrode your equipment as a regular jelly (though if you're in the Slime Pits you should already have a way of protecting against that). Worst of all, it has a unique defense mechanism whereby it spawns additional high-tier slime monsters like Death Oozes and Azure Jellies every time it gets hit, allowing it to easily swarm any enemy player. Also, it's faster than a freaking CENTAUR! To be fair, it should be expected for this monster to be so powerful considering [[spoiler:its existence is literally the only thing keeping the Slime God Jiyva alive]].
** Tiamat. Ye gods, ''Tiamat''. First of all, she spawns in the [[TheVeryDefinitelyFinalDungeon Realm of Zot]], accompanied by a pack of draconians, which are already nasty enemies. Even if you manage to kill off or lure away her draconian retinue, you still have to deal with Tiamat. She has a ''mountain'' of HP and HD, hits like a freight train and tends to come with a good weapon, and worst of all, her scale colors shift - which changes up her elemental resistances and breath weapon.

** The Tomb isn't quite as bad as Hell, but it's still considered to be by far one of the most hazardous of the game's many side areas. It's an undead-themed branch with an Egyptian flavor to it, meaning lots of traps and lots of mummies, most of which will spend their time either smiting you, spamming [[PercentDamageAttack Torment]], or [[EnemySummoner summoning demons]]. What makes it so deadly is the mummy death curse; whenever you kill a mummy, you get hit with some sort of magical backlash. For basic mummies, this just curses a random item in your inventory, but the more powerful ones can torment you, shave off chunks of your health with Pain spells, rot your flesh, drain your stats, or summon demons. In short, mummies can hurt you no matter what you do, and since there's lots of them, this adds up very quickly. If you try to brute-force the Tomb, '''you will die'''.

** Nemelex Xobeh also qualifies if you know what you are doing. The legendary versions of their decks, along with high piety, a decent evocation skill, and liberal use of their gifted abilities essentially turn any PC (even purely melee focused characters) into an epic level mage capable of summoning dozens of creatures in combat with a zero chance of being hostile for a paltry 2 mana or blasting several of the strongest spells in the game better than an equal level wizard could. Plus, you get powers present nowhere else in the game, such as the ability to create food out of nothing. On top of all this, old Nemelex has a grand total of one real rule (using combat oriented cards when there's no one hostile around), meaning the only real way to get excommunicated is to stand around for tens of thousands of turns with out sacrificing anything to them or using cards in combat, something a player is never going to do.

*** The tier 3 demon Neqoxec also qualifies. Though somewhat weak, neqoxecs know (and love to spam) the spell Polymorph Other, which, when used against the player, always gives negative mutations. It's possible to resist this effect with certain equipment, but the neqoxec's status as a mid-level summon means players may end up facing them before they're ready.

** Dragon's Call summons [[InstantAwesomeJustAddDragons dragons]]. [[ZergRush Lots of them.]]

*** Executioners are tier 1 demons (marked in the ASCII version of the game by the number "1") with super speed, which they like to boost even further with the Haste spell. Once that's done they'll zip into melee combat and proceed to hit you like a freight train, often multiple times in a single turn.

** Glaciate has a similarly huge area of effect, does even more irresistible damage than Fire Storm, and slows anything that survives it.

** Jellies. They've got decent HP and hit fairly hard for early game threats, but what really puts them into DemonicSpider territory is their acid. They will corrode your armor every time they hit you, weakening your defenses ''permanently'', and they'll corrode away the enchantment levels on your weapons every time you hit them. If you switch to bare fists they'll corrode away your fists, damaging you almost as much as you're damaging them. Switch to ranged weapons and they absorb your ammunition, often gaining more health back from feeding than you can deal. You can't even run behind a door to escape because they'll just [[ExtremeOmnivore devour that too]]! The only safe way to deal with them is spells, since they can't eat magic. Worse, unlike many others on this list, jellies don't get any less annoying in the late game thanks to their tendency to devour and destroy items laying on the ground. Fortunately they can't devour artefacts anymore, but there are still lots of other magic items that you might want which they can take from you.
*** Jellies are rather less nasty as of the 0.15 changes to the corrosion mechanic. They still eat items off the floor, deal heavy acid damage, and all that stuff, but corrosion now applies a temporary debuff to all your equipment. Granted, having all your equipment enchantments reduced by 12 is pretty horrible, but at least it's not ''permanent''.

** Hydras. Decent speed especially in water, good HP and they're the most damaging monsters in the midgame. They're dangerous enough that if you can't kill them reliably, you'd better avoid the deeper parts of the Lair and the Swamp entirely before you can.

** Mennas the ReligiousBruiser is a late-game boss, and he will KILL your spellcaster (or even hybrid build) very dead if you don't escape in time. The worst part about him is his ability to silence his surroundings, making spellcasting impossible and preventing the most common means of teleporting away (by reading Teleportation scrolls). He's also [[LightningBruiser very fast and very strong in melee]].