Spoiler alert ahead!
The book starts with Huron conquering an imperial mining facility? The lone survivor, an admech priest and her 5 castellans, is persuaded by Huron to surrender and join him at his battle barge. No conversion to chaos needed, as long as she does not give him a reason to kill her. This is of course all part of his sinister chaos plan for her to gradually free herself of her shackles, and in turn be shackled to him.