|This article is about an older version of DF.|
Undead refers to either a zombie or skeletal form of a creature, and should not be confused with ghosts. The undead occur naturally in evil areas, and are typically zombified or skeletal examples of living creatures that would appear in that biome (including carp and other fish, so be careful fishing or fetching water). It is also possible to produce these forms in the arena.
All undead creatures are level 1 building destroyers, unless they were a level 2 destroyer in life.
Zombie is an undead form that can be applied to most creatures. Zombies constantly emit miasma when underground, and they produce a rotting corpse when they are slain. Zombies receive less damage from bludgeoning weapons. Also, they do not bleed, so it can be difficult to properly dispose of them. There have been multiple reports of zombies sustaining all parts mangled while staying "alive." Combat can thus last for a very long time, and a zombie apocalypse is not out of the question should the army fall.
Skeletal is an undead form far more restrictive than zombie. They require the creature to have a bone structure, so creatures like slugmen cannot have a skeletal form. Skeletal creatures produce a skeleton rather than a normal corpse when destroyed.
Skeletons are really tough, having no squishy muscles, nerves or arteries to worry about. Bring a slicing weapon of some sort if you expect to fight skeletons, as slicing off parts is still effective. Alternatively,copper bolts seem to usually kill a large skeleton in 1 hit to a finger. It takes about 5-10 bone bolts to kill a horse-sized skeleton.
Health Point System
Undead have a health point system. In Toady's words: "Undead aren't quite where they need to be yet (skeletons in particular still don't understand how the skull and spine should be holding them together), but they are more killable in this version. Since they don't make sense in the first place, there's a sort of hitpoint system for them now that'll get them dead eventually if you don't break them apart, though punching a skeleton to death takes a long time in this system (...) The undead HP will be revisited once the undead have more of a basis in the underlying reality. (...)"