Life For A Life (Bill Cipher X Reader)

Yeah I know I already have a Bill x reader but I had an idea that wouldn't work in that book so here ya go!
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Twenty Years ago a man was in trouble. He needed help. He summoned a powerful dream demon called Bill Cipher and made a deal. In exchange for his safety, the man gave Bill custody over someone. He didn't know who, until two years later when his daughter was born with Bills Wheel on the back of her neck. It was then he realized his mistake. Eighteen years after she was born, she moved to Gravity Falls Oregon where she finally met the dream demon.