The Witcher Bestiary - Ghoul
Ghoul Occurrence: Ghouls are encountered on battlefields, as well as in cemeteries and abandoned crypts.

Immunity: Resistant to common poisons.

Susceptibility: Sensitive to silver and Necrophage Oil; the Strong Style is most efficient against ghouls; experienced witchers use the Group Style while fighting multiple ghouls.

Tactics: A group of ghouls will try to knock an opponent down, surround him and start eating him alive.

Alchemy: Abomination lymph, white vinegar, and ghoul blood.

Ghouls are said to have been humans who were once forced into cannibalism and, after many years spent in dark crypts, underwent a horrifying transformation. Only human flesh can satisfy their eternal hunger, so they kill people and store the remains in the recesses of their lairs.