Phosphex Bomb

A Phosphex Bomb is an arcane weapon utilised by the military forces of the burgeoning Imperium of Man during the Great Crusade and Horus Heresy eras during the 30th and 31st Millennium. As effective as this horrific weapon was, its use was not widespread as it had a tainting effect beyond even Rad Weapons on the areas in which it was employed, but remained within the arsenals of the Legiones Astartes as a weapon of dire resort.

History
Phosphex was a rare corrosive toxic and incendiary compound utterly inimical of life, deployed both in the form of large canister bombs (Phosphex Bombs) and heavy shells (Medusa Shell). It expands on contact with air into a seething, liquid mist which burns with an eerie white-green flame which is attracted to movement. This gelid flame ignites metal and eats relentlessly into living tissue, and cannot be extinguished short of exposure to vacuum. Though highly effective, this horrific weapon was only primarily used as a weapon of last resort.