Undead commonly occur in three basic types: spirit, flesh, and fleshless. Spirit revenants like the ancestor ghost, wraith, and dwarven ghost, can only be harmed by weapons that are enchanted or made of refined substances such as silver. Ancestor ghosts, the most common spirit revenant, are harmless, apart from the minor curses they lay upon their victims. Wraiths are similar to ghosts, but they are capable of inflicting wounds to the careless explorer. Dwarven ghosts are more dangerous still, but they generally appear only in Dwarven ruins.
Flesh revenants, or 'zombies' as they are often called in the West, are known as 'bonewalkers' in Morrowind. Magic preserves the bonewalker's fleshy remains along with the bones and spirit. Bonewalkers are readily identified by the sharp protuberances of bone and metal employed in the rituals that bind them to this plane. All bonewalkers are malevolent and dangerous, but the greater bonewalkers are far worse than the more common 'lesser' bonewalkers. Thankfully, normal weapons harm bonewalkers.
It is difficult to generalize about fleshless revenants, or skeletons. The agility and fighting ability of the animated remains may depend on the abilities of the revenant's former life, and may therefore be weak or strong, or more or less capable with weapons and shields. Fortunately, enchanted weapons are not needed to destroy skeletons. An exception is the bonelord, a peculiar form of revenant that seems to derive its powers more from its spirit energies than from the substance of its skeletal remains. Bonelords are very powerful, and very dangerous. Normal weapons do not affect them.
Vampires were believed to be extinct in Morrowind for centuries. Dunmer culture has a special hatred for vampires, and in earlier times the Ordinators and Buoyant Armigers hunted them to extinction. In recent years, however, vampires have either begun to sneak into Morrowind, or long-dormant ones have been awakened. Vampires vary in their substance and power according to their age and accumulated lore, but even the weakest vampire is immeasurably stronger than most other undead. Note: Ash vampires are not vampires, and are not undead. Ash vampires are extremely dangerous. While their spirit and substance may indeed be preserved by some magical process, the holy warriors of the Tribunal Temple report that spell effects known to affect the undead have no effect on ash vampires.