The Other Side of Hell — Niall Teasdale

In the final battle with the dragons, Lily Carpenter sacrificed herself to save Ceridwyn Brent, and the world. There was not even a body to bury; she vanished in a blaze of light leaving Ceri to mourn her passing. Then a revelation suggests that Lily might not be dead, just elsewhere. But even for one of the most powerful magicians since the Shattering, walking into Hell to get her back may be one journey too far.