Satan has put his seed in your sister. She's made a deal and now she is Satan's Daughter. She's gotten rid of your girlfriend and wants you. You will be hers. You cannot resist her powers. She's able to seduce you like the Succubus she is with only a single look. She tells you that she will share the powers with you if you breed her. She wants a taboo relationship with her brother and she went so far to get it