User blog comment:40kfan/A Community Project Idea (god help us all)/@comment-32788838-20141126222314

One idea I had was a Chaos Witch who basically serves as the Dark Covenant's equivalent to a Joan of Arc figure; a former Primaris Psyker and Inquisitorial retinue member who was corrupted some time ago - probably a few centuries back, a millennium at most - who had once assisted the Inquisition due to her powers of precognition, as she could allow for threats such as Space Hulks and Chaos cults to be prepared for before they even arose or appeared, alongside other powers and abilities that a Primaris Psyker would have, which I still gotta think about.

After the death of her Inquisitorial handler and the rest of their retinue upon fateful assignment that she had precognized at the hands of a powerful Chaos cultist leader, she would manage to execute the traitor with her psyker abilities and not long after fall to Chaos. However, I want to give her interesting reasons and justifications for her betrayal to the Ruinous Powers, reasons that are more than simply "possessed and mind controlled" as it would oppose against the philosophy of the Dark Covenant, which is based on strength, and how she would have come to garner and maintain a warband of Chaos cultists and followers of her own.

As for personality, I'm imagining it's primarily based on her reasoning for turning to Chaos, although I'm imagining she's a stern, dominatrix-like figure (not in the Slaaneshi way mind you, if just ever so slightly) who isn't afraid to get her hands and/or claws dirty when faced with combat and letting other members of her group know she's the boss.