A Primaris-rogue Witch is an unsanctioned psyker within or without the Imperium of dangerous psychic potential. Many are affiliated to the Ruinous Powers. Sometimes primaris-rogue witches lead Chaos Cults and some are even the demagogue-leaders of warbands of the Lost and the Damned. The most miserable of these creatures are open portals for the powers of the Warp, forming doorways into the mortal world and potent pawns whose powers are easily twisted to suit the Neverborn's malevolent ends.
A famous instance of the insidious power of such rogue witches occurred on Thracian Primaris in 338.M41. There the rogue Inquisitor Quixos instigated in secret an act of violence during the Triumph of Warmaster Honorius, Honorius having completed his purge of the Ophidian Sector. The Triumph was overseen by Lord Commander Helican, as all the survivors, corpses, relics and important prisoners of the Ophidian Campaign processed through the hive. Quixos's plan was to steal one of the thirty-three psykers captured during the war, but the attack resulted in the release of other rogue witches who proceeded to ran rampant through the hive. The powerful abilities and venemous will of these Chaos witches resulted in the deaths of tens of thousands of formerly jubilant citizens, inquisitors, Arbites, Astra Militarum soldiers and many of the Aurora Chapter of the Adeptus Astartes.
- Imperial Armour Volume Thirteen - War Machines of the Lost and Damned, pg. 152
- Malleus (novel) by Dan Abnett, chapters 5-8.