The Last Enchantment (Arthurian Saga Series #3)

"The richest of the three...mighty...climactic...action and supsense constant, even harrowing."
THE WALL STREET JOURNAL
Arthur is King! But while unchallenged on the battlefield, sinister powers plot to destroy him in his own Camelot. When the rose-gold witch Morgause, Arthur's half-siser, ensnares him into an incestuous liaison—and bears his son, Mordred, to use to her own evil ends—a fatal web of love, betrayal and bloody vengeance is woven.