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Stripped of her dignity, identity, and freedom upon being placed in a man-made prison of concrete and steel, a female inmate known only as Sigma bides her time until she can finally strike back against her jailers and reveal the true goal of her deadly mission. There was a time when Sigma had a name, and a sense of humanity. But within these walls there exists no humanity, and the only name you know is the one that you are forced to take. To be in this penitentiary is to fall prey to an ancient, invisible evil. The sadistic guards and the corrupt wardens may be merciless, but the force within these cold and damp walls seeks to swallow Sigma's very soul. Sigma is on a mission to confront this dark force, and no single human possesses the power to hold her back. Now, as female prisoner Sigma prepares to come face to face with the evil that has claimed so many lives before her, a woman once reduced to prey transforms herself into the ultimate hunter.