Ghost in the Blood - The Ghosts, #3

Caina is a Ghost nightfighter, one of the Emperor's elite spies and assassins, and few enemies of the Empire ever escape her cunning. Yet all Caina's wit and skill might not be enough to save her from a terrible fate. Sent to hunt down a cruel slave trader, Caina encounters something far darker. An ancient evil, a thing of legend and terror. A creature that wants to corrupt her, heart and soul.