Ep 1. Be Deviled

Sin, in the form of Serena, goes to visit Hercules. She tells Hercules she needs his help to capture Xerxos, an escaped murderer from her realm of evil. She is secretly in league with Xerxos, and poisons Hercules, so Hercules has to take power from her to fight Xerxos. Her power slowly turns Hercules into a demon and Hercules becomes more and more evil by the second.