The Inquisitor sat in his chair, viewing the chamber where the Cultist was being purified. This was experimental; never before done in, as far as he knew, any of the history of the Imperium of Man. The heretic lay in the centre of a pentogram, with Grey Knight Librarians at each corner of the star.
Grigoriy Russ gave the order for the ritual to begin. He looked down onto the cultist chained in the center, and spoke in a voice which would have made regular Slaaneshi cultists "Repeat after me these phrases, girl. They shall mark your purification.
"A corrupted heretic, stained am I." With a resigned sigh, the cultist repeated the Inquisitor's words. "A corrupted heretic, stained am I." She'd really miss the fun of Slaanesh worship.
"My soul corrupt, I offer to Him on Terra." Russ said, motioning to the Knight Librarians. They as one focused harder, and what looked like black steam started streaming from the Cultist's ears and nose.
"My soul corrupt, I offer to Him on Terra." She repeated