Apollyon (The Fourth Covenant Novel)

Enter the world of Covenant...Alex has Awoken and become the Apollyon. She has connected with Seth and now the thing she feared most has happened: her true self has been lost. But love is stronger than fate, and Aiden St. Delphi will do anything to break the connection and get Alex back. And then there's the fact that the whole Alex-and-Seth combination is pretty dangerous: if Seth drains Alex of her power, he'll become the God Killer and the most powerful being on the planet. The one person needed to stop the impending destruction has been dead for centuries - and Alex will have to search for him in the Underworld. Finding her way into the Underworld to search for one soul among countless millions will be hard enough. Returning will be even harder. Alex needs to prevent Seth from becoming the God Killer...but the cost will be higher than she ever imagined.