Ghouls
Thus far, the only ghoul to make an appearance in any Discworld novel is Sister Drull of the Fresh Starters. Described as a shy old woman in a shapeless grey dress, it is uncertain whether she eats dead human flesh as a traditional ghoul, but it is confirmed that she is a terrible cook. Commander Vimes briefly suggests allowing a ghoul to work in the forensics department of the Watch, provided that the ghoul doesn't take anything home to eat.
Read more about this topic: Undead (Discworld)