Highlord of Darkness, Book 1, Highlord of Darkness Series — Christine W. Murphy

Narragan is supposed to be bad. It's expected. On Orgon, it's the religion. But he doesn't feel like the latest incarnation of evil. He's just an average guy who doesn't get along with his father, has thirty sisters to protect, and writes really bad poetry. If he doesn't learn how to be bad soon, if he doesn't figure out how to become the Evil One, then everything and everyone he loves is doomed. If Narragan doesn't want to be responsible for the end of civilization on Orgon, he has to become the Highlord of Darkness.