Black Essence

The Black Essence is an apparition seen only with Witchsight. It is not so much an independent creature as it is something that seems to hang about the living. Preceded by a moist stink of decay and cloying brimstone, the black essence appears suddenly. Wherever the caster looks, he sees foul clinging darkness spilling out from eyes, nostrils, and mouths. Even when no one’s around, the caster sees pools of this filth in puddles on the ground, dripping from the walls, staining plants and so on.

Also Known As: Creeping Darkness, Foul Aura, Mortal Doom

Attracted By: Dark Magic, Necromancy, Foul Rituals

Source

 * Warhammer Fantasy RPG 2nd ED -- Tome of Corruption pg. 208