A rogue psyche turned into a primaris psycher for the Stygian Guard. The Stygian Guard made extensive use of rogue psychers in combat. While some were used for divination or pyromancy, the vast majority were used for summoning daemonic aid in battle.
While this vastly increased the striking power of the Stygian Guard it also led to an extremely high mortality rate amongst the rogue psychers accompanying them. Fortunately for the Stygian Empire they had a large pool of such psychers to draw upon both from within the empire and from those fleeing persecution from the Imperium.
A small handful of psychers were use as astropaths and even as intelligence gathering assets if they showed any skill in telepathy. Many an Imperial secret was betrayed by the prying of an unguarded mind. A very few select handful became hosts for Daemonic entities. These host psychers became talismans for the chaos worship within the Stygian Empire. On the battlefield they wielded immense psychic power and provided beacons of faith for the Stygian Guard.
Such host psychers were easily identifiable due to mutation of the host from the daemonic entity. The mortality rate amongst these psychers tended to be very low, in part because of the daemonic influence that coursed through their bodies. Often when the host psycher died it was in transformation to a greater daemon on the field of battle. In such a instance the loss of the psycher was easily excused due to the increase combat power the greater daemon brought forth. Furthermore the increased use of psychers especially those wielding malefic powers added to the turmoil of the warpstorms surrounding the sector.