Chaos Cult - Slaves to the Void: Although the Word Bearers often employed the many Warp cult forces aligned to them as auxiliary soldiery, their greater worth was as a mass offering to the Warp entities to which they were dedicated.In the aftermath of the Isstvan V Drop Site Massacre, the Warmaster Horus had tasked Lorgar and his brother Primarch Angron with engaging the Ultramarines on the Eastern Fringe and ensuring that the XIIIth Legion was not able to interfere with the Traitors' march on Terra. Lorgar intended to achieve this by two means: one military, the other far more esoteric.The military objective was to unfold during and after the Battle of Calth, once the Ultramarines' strength had been shattered by the surprise assault of the Word Bearers forces. In this, the Warp cultists aligned to Lorgar played a support role, for the task of killing Legiones Astartes could only be performed with any true efficacy by other Astartes.The Warp cultists' role in the Battle of Calth was to engage the mortal forces mustered on and about Calth -- the native defence units, Imperial Army line regiments and the elite of the Solar Auxilia.They were used as cannon fodder by the Word Bearers, hurled against a thousand defensive positions in order to foul the defenders' guns while the Traitor Astartes closed to assault range to deliver the killing blow.They were then used to hunt down survivors of the initial betrayal and to harry any force that attempted to consolidate with other remnants and were given responsibility for scouring the cities of Calth of their populations, driving the populace from the shelter of the dense cities and into the killing fields directly under the guns of the Word Bearers' planetary bombardment fleet.As much as these tasks represented a military objective, they each served a still greater end which not even the genius of Roboute Guilliman could foresee. The deaths inflicted by and upon the numerous Warp cults aligned to the Word Bearers were all enacted as part of Lorgar's great ritual to bring about the Ruinstorm -- a vast Warp Storm similar to the later Great Rift that was to reave its way across the stars and slice the Imperium apart.Every drop of blood shed by the Warp cults, whether that blood was their own or their enemies', served to attract the attentions of the Ruinous Powers. Each scream resounded in the Empyrean and added yet another note in the great symphony of Chaos which only Lorgar could perceive and direct. That symphony was building to a crescendo that was to break many solar months later at Nuceria during the climax of the Shadow Crusade.Though it might appear that the Word Bearers' allied Warp cults were brutally exploited in the pursuit of Lorgar's grand scheme, the truth must be that they were entirely willing participants in their own demise. The cultists had been promised all manner of esoteric and visceral rewards in return for their lives.These religious fanatics willingly threw themselves onto the enemy's guns, in the process achieving the multiple goals of soaking enemy fire, blocking shots aimed at their Legiones Astartes masters and of proving themselves worthy of the rewards promised to them.They did so with evident fervour, shrieks of blasphemous ecstasy on their bloody lips even as they fell, a pattern of behaviour still seen in the present day among Chaos Cultists.A further, still more awful, use which the Word Bearers' cultic allies were put to was only suspected at the time and was uncovered in more detail during the long years of the Calth Underworld War. The cultists were used as sacrificial offerings to the Ruinous Powers, willingly setting their necks upon sacrificial blocks or shedding their guts upon stone altars as part of the most hideous and debased Chaos rituals imaginable.The objectives of these rituals varied, and while some were component parts of the larger ritual to bring the Ruinstorm into being, others were intended to summon Warp entities -- only later named "Daemons" in common Imperial parlance -- from the other-dimension of the Warp.The more ritual form the deaths took, the more powerful or more numerous the entities summoned, so that for a time at least, the raw stuff of reality became stretched and worn at Calth as the things brought forth by the Word Bearers fell upon their mortal prey in an orgy of blood.Oftentimes, those cultists not slain during the summoning of the Warp entities were butchered by them soon afterwards, serving as the sustenance the creatures required to remain in the material dimension and fuel the planet-wide slaughter to come.