Wraith corpses should function as a potion of gain level does, of the same beatitude as the corpse. I.e. a blessed wraith corpse will gain a level and then some fraction of experience points towards the next level.
Occasionally, when a bones file would create a ghost (e.g. most times), and the level difficulty is high enough, create a wraith of the player instead. If in Gehennom, occasionally create a shade of the player.
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.
F corpses can be dipped into potions to make different potions: juice + violet fungus = booze, juice + yellow mold = sickness, water + green mold = acid. (Note the existence of the Brewing Patch, which dissolves most F in juice to produce confusion, hallucination, booze, sleeping, and healing.)
Later suggested recipes which involve dipping a corpse in acid to dissolve it:
Make the Castle not a graveyard level, and compensate for this by altering wraith corpse drop odds somehow.
Wraith corpses cannot give food poisoning, though they can still rot away.
