[Elanorea]

Yeah, dwarves can come back from the dead in two ways - as ghosts and zombies.

Ghosts are mostly just nuisances, unless the dwarf was berserk when it died, in which case the ghost will kill or maim dwarves at random. Ghosts can't be killed or harmed physically and will only disappear if you bury the dwarf or make a memorial for them.

Zombies will rise automatically from any corpse left on "evil" terrain and can be killed with weapons or traps, though if a zombie is killed and the corpse is left in the evil area, it will rise again. Severed body parts such as hands or heads can also become undead.

Of course, if a dwarf is turned into a zombie, its spirit will likely also rise as a ghost unless you make a memorial for it, since the walking dead generally won't agree to be buried. Double the fun!