Spellfire by Jessica Andersen

Imprisoned and tortured, Rabbit knows that even if he can escape, there is no going back. Although an ancient prophecy says his unique powers are key to winning the Nightkeepers' final battle, he's lost his magic.

He has betrayed the one woman he loved and although he wants to make amends, Myrinne's not prepared to face the fierce man he's become or the dangerous feelings he sparks in her.

With a xombi outbreak in the human workd, Rabbit and Myrinne must forge a new partnership amid the threat of worldwide instability and an undead army. Rabbit must master his ferocious magic--or all will be lost.