While many Cults lack the expertise to make or the access to steal large supplies of Frag Grenades, it is very easy for Brood Brothers to create their own home-made incendiary devices from small (usually glass) containers of flammable liquids. Hurling them at enemy units in cover, the resulting flames buy some time as the Brood Brothers advance into Assault. The Cult uprising on Moltov Prime saw these used to great effect. The planet's more famous fermented products were turned into thousands of lethal projectiles in the bid to overthrow the entrenched aristocratic government, and the battle cry of "Let them Drink Moltov Cocktails!" was heard throughout the capitol city.
Firebombs in game play work exactly like Frag Grenades, but the resulting flames prevent any assaulting Cultists from Advancing; any Cult units involved in that Assault may only Consolidate. Firebombs are also more bulky and unwieldy than regular grenades, so they can only be used once per game.