The Exploding Sky — Kimberly Loth

Gabe is in Samir's clutches and Liv has no earthly idea how to find him. She could kill Samir, but that's only if she gets close enough to him and she can't freaking do magic. But, Gabe can escape, right? Sure. Except, Samir finds a way to threaten Liv from afar and now Gabe has to do everything Samir asks him to. Including killing goddesses. Read the final book in the series, The Exploding Sky, to find out if they can find one another again and take out Samir once and for all.