Xenogenic Acid
From Warhammer 40k - Lexicanum
The Xenogenic Acid is a Bio-Artifact of the Tyranids.[1]
This oily black substance continually seeps from the swollen cysts of its carrier. Splashes of the liquid have been seen to flow against gravity towards horrified eyes or compromised armour plates, giving rise to speculation that the acid itself is sentient. Within moments, the horrifying acid finds its way inside its victims, breaking down its genetic and molecular structure until all that is left is a bubbling pile of black bio-matter.[1]
