The Silent Messiah. More commonly called Mistress Nine. She is the deamon that will bring about the end of the world. And her host is inocent Hotaru.
Hotaru is posessed. It was an exchange in a deal made by her father. To save her life he had to give her, and himself, to a great evil by the name of Pharoh Ninety. When the time is right, Hotaru is forced to give up her body to her unwanted guest.