To save his brother's soul, Casimir Warlin exchanges his own to a nefarious rogus, one of countless demonic entities that plague this world, and becomes forever bound to serve her in secret. In a cruel twist of fate, he learns that he was born with the rare abilities bestowed among venators, who exist to keep the rogus at bay. When Casimir enrolls into a venator's academy, he risks his secret and endangers the souls of his new friends against his will. It's the ultimate betrayal, but it's part of the deal.