Undead are creatures who have died, but been reanimated through dark magic. The creation of undead has, historically and in the present, been forbidden in pony society. That said, since the Catastrophe, enforcement of laws and customs forbidding necromancy has been sporadic.

There are various kinds of undead. Skeletons and zombies are not intelligent, and do not bind the souls of their former owners; the creation of these sorts of undead is considered highly distasteful but not intrinsically evil. However, many mages consider these "gateway" undead that may tempt the practitioner to dabble further, particularly in ghosts and revenants .

Ghosts are (usually) pony souls bound to the material plane through magic. Ghosts do not typically occur naturally; pony souls normally depart expeditiously for the afterlife upon the death of their host. Necromancers cannot forcibly retrieve souls from the Afterlife, so ghosts must usually be created at the time of death. (Souls can sometimes be tricked into returning, but this is apparently difficult.) Ensuring the availability of the moribund is not usually not a major obstacle for the flexible scruples of practitioners who would create ghosts. Ghosts are sentient and free-willed, but usually bound to the necromancer. As they are incorporeal, they can neither harm others physically nor be harmed by weapons or other forms of physical damage.

Other sorts of undead are sporadically reported. Given the limited amount of credible information on even the relatively more common types described above, it is difficult to draw reliable conclusions about the abilities of these.

In PRPG1, Dusty Tomes had become a lich (a skeletal, sentient undead creature) to survive his imprisonment in the Arcane Helix by Eldritch Lore.