If you kill a pet whose species has a zombie counterpart, a zombie of that pet may appear later to try and kill you.

Meleeing monsters while you are afflicted with a zombification disease will start zombifying them.

Buff zombies, to make them more of a threat. Import FIQHack zombification (a zombie bite will place you 90-100 turns away from turning into a zombie, each additional bite decreases the timer by around 10 turns, but it will go away by itself if the timer doesn’t dip below 40); boost their difficulty, but keep their HD low; allow them to revive themselves less frequently than trolls, but also revive themselves whenever another zombie steps over their corpse.

Add a monster species flag for “zombifiable”, and track zombification or mummification as flags on an individual monster, removing the need for Z or M to be separate classes.

Amulet of zombification. Increases your zombification counter while you are wearing it. Taking it off cures the zombification.

Buff late-game undead, because undead’s significance in Gehennom tends to be pointless since they aren’t scary by the time the adventurer gets there.

• Zombies can resurrect in Gehennom akin to GruntHack zombies.
• Spectres, which are like wraiths but much faster and with more attacks.
• Vampire mages.
• Skeletal dragons.
• Minotaur zombies.
• Z might need to be made ungenocideable.
• GruntHack-like zombies, which inflict zombification sickness and eat your brain to drain Int.
• Shades can generate in graveyards in Gehennom.