The Trinity Cult.
tl;dr
Mexican Female-Jesus ("Trinity") used magic to force gods to submit to man kind, in the name of one powerful god (often identified with YHWH). After which, she left a book of magic teachings and was taken to heaven. Many gods became demons, opposing the extreme god. (Assuming this happened after the Tower of Babel)
Her father started the cult, and she claims he had the book. She actually adopted me for the purpose of teaching me magic and making me take over the cult, when she's too old, or passing away.