Zombies should be able to pick up and put on mummy wrappings they find on the ground, which instantly turns them into their corresponding mummy.

Zombie arm, which is occasionally dropped by zombies. It can be wielded directly as a club, or you can equip it with a weapon which gives you the ability to melee targets from a little farther away. Eventually rots away with the same timer as a corpse.

If you try to sell a zombie corpse to a shopkeeper, they get angry. Or maybe they merely won’t let you into the shop if you’re carrying a zombie corpse, the same way it works with digging tools.

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.

Zombies can’t open doors, but if there are multiple adjacent zombies on one side of a door, they can bust it down.

Whenever a zombie steps over a zombie corpse, it revives.

Zombies and possibly mummies have a new sound MS_GROAN instead of MS_SILENT. This would not do anything at the moment except give you “The zombie groans.” when chatted to.

Zombies destroyed by turning never leave corpses, or the corpses they do leave are incapable of reviving.

Not all zombies are hostile; only the hungry ones are. Thus, some zombies might be generated peaceful. However, a nonhungry zombie has a small chance of turning hungry each turn.

You can pray at a gravestone, or possibly ring a bell at one, to cause any of a number of good and bad effects:

• Summon a ghost, which might be hostile or peaceful.
• Summon a hostile undead, flavored as it forcing its way up out of the grave. Usually a zombie.
• Polymorph you into a zombie or mummy of your own race.
• Put you to sleep, ignoring resistance.
• Create a swarm of hostile manes or lemures.
• The headstone falls on your foot, dealing some damage, less if wearing boots (“killed by a falling tombstone” if fatal).
• If the grave is a bones pile grave, the ghost of the player always appears. It will be peaceful if their alignment matched your own and hostile otherwise.
• Various cosmetic messages that do nothing. “The air suddenly turns cold.” “The engraving on the headstone shimmers for a moment.” “A shiver runs down your spine.”
• The dirt cracks open and spits out any items buried under it.
• A voice from nowhere whispers a random rumor, true or false.
• The epitaph on the grave changes. This does not flag the grave.
• Get an alignment bonus for honoring the dead (this is only if triggered by praying). “You feel that the one buried here is content.” Bonus might be larger if you’re lawful or a Priest, probably 1 otherwise. This should possibly happen before and independently of any other effects.
• Limited identify of 1 item.
• Type-identify of multiple un-type-identified items in the inventory, but the player doesn’t get to pick which. Might pick 0 items (flavored as the spirit not knowing anything new about what the hero is carrying).
• Enlightenment.
• Temporary telepathy / sleep resistance / infravision / other intrinsic.
• The gravestone rumbles and moves aside, revealing a branch staircase to a just-created-now one-level branch, a small one-off “crypt” floating branch that contains some undead, some boxes containing corpses, and some treasure. This only happens on gravestones in the Dungeons of Doom.
• You “feel that the dead are restless”, aggravating monsters level-wide. All gravestones on the level become flagged against further attempts. This effect could be added to and independent of other ones, and if so, it’s a chance dependent on the number of already flagged gravestones on the level, which provides a nice way to balance it on levels that have massive amounts of gravestones.

After you get one effect, the gravestone is flagged so that it doesn’t happen again (or, more evilly, that any further attempts will only result in bad effects). Possibly shouldn’t work at all on graveyard levels, because they have too many graves to balance these effects.

If a zombie finds a mummy wrapping, it will pick it up and transform into a mummy of that type.

Mind flayers have to grapple your head before they can successfully suck your brain (like in D&D), forcing them to spend a turn doing this. If you have a greased helm, this gives you at least one extra turn to act since they will not be able to grapple your head until the grease dissolves.

This would probably best be implemented by giving them a sticky grab or bear hug attack and ignoring the existence of their tentacle attack if they aren’t already grappling you (or you are being held by another enemy and thus can’t avoid them). Either way, checking u.ustuck is the key.

Possibly, they need to spend another attack getting your helm off, which will unequip it, though this will get weird if your helm is cursed. A cursed helm shouldn’t offer total protection against them. Possibly, they should be able to remove a cursed helm (like nymphs and foocubi do) despite its curse; this could be handwaved as them using their psionic powers to do it.

In variants that implement zombies eating your brain, it should work on basically this same system, where the zombie needs to hold onto you before it can eat your brain (and which also works that way in D&D).

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.

In variants with reviving undead, you can apply a weapon downwards at a dead zombie’s corpse to destroy it so that it can’t revive. This may take several turns.

Zombies always try to path in a straight line towards the player (assuming they can see or otherwise are aware of the player), and get stuck on terrain.

Change zombies’ and possibly mummies’ claw attack to a bite attack.

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 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.