The various freaks and creeps from the original Splatterhouse trilogy will show up in evil biomes to torment your dwarves. There are also four megabeasts that will seek you out regardless of where you are - show them why we call it the Splatterhouse!
Deadmen - the most basic zombies, only more nasty-looking - completely fearless, tough to debilitate, and while weak individually, they mostly show up in groups.
Body Eaters - horrible, corpse-eating worms. Even more pack-oriented than the deadmen - they pack a mean bite.
Top-Heavies - strange demons with bloated heads. Larger and stronger than deadmen, but not by much - still a fairly basic enemy.
Nobu - these small slug-like things will spit acid at your dwarves, causing bleeding and blisters. They can bite with their strange maws, but due to their size it will not be particularly effective - they also do not leave bodies behind.
Oba - tiny, unformed demons. They don't even have bones or teeth - while very weak individually, they always show up in groups of atleast 4, up to 12.
Master of the Dead - what a name. And what a guy. He will float around, and if there's any corpses nearby, he will raise them as zombie minions. Unlike regular necros, he'll raise even completely mangled and mutilated bodies. Better keep that corpse stockpile hidden away! Also, on death his body completely disappears, leaving only his stylish, human leather hat behind. Thankfully, they're uncommon.
Biggy Man - this big lug appears rather uncommonly. But if he does, watch out - he can easily turn dwarves into hamburger meat with his chainsaw arms - aside from that however, he doesn't have any other gimmicks. If you hear the sound of chainsaws revving while exploring evil biomes in adventure mode,
run.
Screaming Mimi - experimental, eyeless things. Slightly larger than humans, they mostly attack with scratches and bites - in adventure mode, their presence is signaled by shrill shrieks. That said, they are not fond of water, and will drown should you knock them into even a shallow pool.
Bellyache - this big, fat thing appears uncommonly. It is surprisingly agile - however, its gut sack serves as a weak point, and cleaving it will always spill its guts. That is, if it lets you get close to it - at a distance, it spits globs of acid - up close, it will bite, scratch and punch dwarves - its most deadly attack however, is a slow tackle with their entire body weight - it leaves them highly vulnerable should they miss, however.
Metamorl - eyeless, long-tongued things. Fairly agile, they attack with kicks, lashing with their tongue, headbutting or simply punching or scratching; they are also good at dodging. If you take too long to finish one off after damaging it even slightly, they will transform...
Four-legged Metamorl - the transformation of the above - it trades body size for increased speed. They will also bite, kick and occasionally tackle dwarves while in this form.
Hellworm - fliers found in groups of 2 up to 5. They are rather fragile, since their main body aside from the head is made out of brain tissue. However, they pack both a mean bite and a deadly headbutt.
Lake Horror - only found in evil lakes. These large monstrosities are content sitting at the edges and pelting your dwarves with projectile spines.
The Corrupted - the following creatures, up until the Gorehound, are all considered the same "species", being merely different castes. As a result, you'll see them pop up in mixed groups.
Borndead - the lowest form of the Corrupted, being merely a mutilated corpse inhabited by a demonic spirit. It attacks with kicks and swiping with its bloodied stumps.
Dead Ripper - a common form, larger than humans. Seemingly related to Screaming Mimis, they do not however share the same weakness to water.
Devourer Demon - fat demons, whose bites are incredibly powerful - they can also do a headbutt that is also rather deadly.
Charghoul - burned demons with melty faces - while not any stronger, they are however more resistant to damage than the other types.
Biter Demon - handless demons - while its not visible, they have a long tongue and can lash with it. Their bites, while not as deadly as those of the Devourer, are still above those of the other Corrupted.
Pretender Demon - one of the most rare forms of the Corrupted. These long-armed things mostly attack with scratches and punches - the former are quite deadly - they also can attack with a tackle using their full body weight. They also can taunt your dwarves with vulgar gestures, making them more rage prone and violent.
Foul Beast - the most rare and resilient of the Corrupted. They are the largest, and most adept at combat. Worse yet, they can survive without a head, and hide a third clawed arm inside of their main body.
Gorehound - dog-like things. They can spit up their own stomach acid - that pile of mangled intestines on their underside also houses a stinger that they can use for inflicting piercing damage.
Death Worm - these worms are fairly uncommon, but are also rather deadly. They stab with their front legs, and can also bite - their main ability, however, is releasing bursts of lightning that can cause paralysis.

Boreworm and
Mindless Beast - the Boreworm functions like a night troll in worldgen, setting up a lair, kidnapping citizens and turning them into Mindless Beasts. However, they can also be found very rarely in evil biomes.
The Boreworms attack mostly with bites, headbutts and tackles - the Mindless Beast has most normal humanoid attacks - however instead of scratching it stabs and slashes with its retractable claws.
For gameplay purposes, the male and female Boreworms are considered different species.
Megabeasts
Hell Chaos - a colossal, undead abomination. While in the original game, it was burrowed into the ground and you could only see its head and arms, here it comes out in its entirety. It lacks most organs besides the heart, and is really tough to debilitate - aside from that, it doesnt have any gimmicks besides hitting hard.
Ultimate Evil - this grotesque mass of flesh attacks with bites and slow tackles. It is also capable of shooting a single ball of hardened flesh that can cause strong blunt damage - or alternatively, several screaming heads that are weaker but can hit multiple targets.
Evil One - a crystalline, colossal demigod. It uses bursts of lightning, similar to those of the Death Worm, and fireballs. It also has a fleshy internal head that occasionally pops out for a biting attack.
Terror Incarnate - the physical incarnation of terror itself. It attacks with punches, scratches and headbutts - it can also launch screaming souls as a strong, blunt projectile, and also fire off fire streams. On death, it does not leave behind a corpse - instead, it drops a certain familiar mask...It provides excellent protection for the head.