Fury of Chaos
Unlike many of the daemons studied by the Ordo Malleus, Furies do not belong to the hosts of the four unholy powers that dominate the warp. Reputedly formed from the souls of mortals who tried to draw on the power of Chaos without swearing allegiance to one of the Ruinous Powers, these unclaimed daemons are doomed to endlessly wander the Immaterium in a state of endless, meaningless existence. Furies are barred from entering any of the Realms and must contend with the tumultuous storms of the Immaterium on their own. Weaker than most other daemons, which often enslave them for their own uses, they are nearly-mindless manifestations of Chaos in its purest form.
When the Crew interrupted the Chaos Cult that they had found hidden away within the Macrostatue of the God-Emperor on Footfall, whatever they had been planning to accomplish went terribly wrong and summoned a massive Fury of Chaos when a score of the cultists, including their leader were gunned down.