Warpstone

Warpstone is a fictional mutagen found in the Warhammer world, and also in the Warhammer 40,000 universe during the first and second editions. Humans and most other races refer to it as Wyrdstone.

Warpstone is solidified Dark magic (Chaos Energy, aethyr), and as such it holds tremendous transmutatory and alchemical powers. In its unrefined form, it is a stone that emits “blackness”, appearing to swallow all light from its surroundings, and so creates a patch of darkness around itself that makes it impossible to see its exact shape. It is sometimes described as “still emitting its own green glow”, which would result in a rather complex optical illusion.