Flight into Darkness — Sarah Ash

As an impulsive young man, Rieuk Mordiern accidentally freed Azilis, a guardian spirit charged with keeping the balance between the kingdoms of the living and the dead. Now Rieuk's sole purpose is to bring Azilis back -- only she doesn't want to return. Instead she has attached herself to a very talented mortal, the renowned singer Celestine -- becoming, as Celestine believes, her personal guardian.

Celestine has never needed a guardian more. Her desire for revenge against the people who consigned her magician father to the flames is leading her down a dangerous path. And chaos is growing. Seven daemons from another realm are now threatening to lay siege to the mortal world. Now both Rieuk and Celestine must discover what it means to truly be a hero.