The Tome of Decay (2014), p44 — Decaying Armoury

Foulswarm Grenade

As lethal to create as they are to use, Foulswarm Grenades contain a foul concoction whose true nature is known only to the most pox-blessed Plaguemeisters of the Screaming Vortex. Sealed with wicked alchemy and fell curses of rot, these weapons produce an acrid, seething haze upon detonation that drifts outward like a ravenous cloud of flies, inexorably enveloping and putrefying everything it touches.

Whenever a creature begins its Turn in the cloud of smoke created by the Smoke Quality of a Foulswarm Grenade, it suffers a single automatic hit that inflicts 2d10 Impact Damage with the Corrosive and Toxic (3) Qualities.

† This weapon has additional rules. See full rules for more details.