Spell of necromancy that turns a corpse you’re standing on (or possibly adjacent to you) into a tame undead. Probably in the clerical school, though a case could be made for matter (and certain variants have a school of necromancy which this would much more directly fit into). It will work on corpses of undead that you have killed. Casting this spell would have some sort of penalty for lawfuls; there would be some sort of warning before trying to cast it.

You can normally only create zombies or mummies when an undead monster exists for the kind of corpse you are animating (i.e. a jackal can’t be turned into undead but a gnome can turn into a gnome zombie/mummy). For intelligent monsters that have no counterpart, the spell can create ghosts.

At a high enough skill or caster level, you can create skeletons from the corpse of any vertebrate, and maybe even vampires from humanoids. You can also create wraiths and shades from monsters that have no undead counterparts.