Blood Fruit

Native to the Bastion Stair, Blood Fruit resemble a wan, black, malformed apples and are tautly filled with a mixture of blood and oily, dark ichors. Eating a Blood Fruit wracks the body with terrible mutations, which occur over the course of a week if not immediate. Once plucked from its vile source, a Blood Fruit loses its potency and becomes completely inert within a month's time. These fruits are prized by Chaos Sorcerers for use as ingredients for spells and rituals.

Source

 * Warhammer Fantasy RPG 2nd ED -- Tome of Corruption (pg. 205)