Daughter of the Blood By Anne Bishop

The Dark Kingdom is preparing itself for the fulfillment of an ancient prophecy–the arrival of a new Queen, a Witch who will wield more power than even the High Lord of Hell himself. But this new ruler is young, and very susceptible to influence and corruption; whoever controls her controls the Darkness. And now, three sworn enemies begin a ruthless game of politics and intrigue, magic and betrayal, and the destiny of an entire world is at stake.