Ghouls are undead, so they are immune to sleep, charm and hold-based spell effects, they do not need to check morale, they can be turned by clerics and paladins (see the OSRIC rules for the relevant tables), and they take 2d4hp of damage from flasks of holy water.

Like all undead, ghouls do not heal naturally. An injured ghoul can recover 1hp per night, but only if it feeds on a corpse at some point during that night.

The touch of a ghoul causes dwarfs, gnomes, half-elves, halflings and half-orcs (but not elves) to be paralysed for 3d4 rounds. A successful saving throw vs. paralysis enables the target to avoid this effect.

Any human killed by a ghoul will rise from the dead as a ghoul itself. This takes place 1d6 hours after death.

Variants:

Like all undead, ghouls do not need to breathe, so they are sometimes encountered underwater.

It may be possible for some animals or monsters to become ghouls. In particular, certain areas are known to be haunted by ghoul stirges.