Redemption - Evans S. Usher

Jack has been taken to the Underworld by Bael. With no other options, Cam and Anya set off to Mexico City to tangle with the noxes, hoping to charm or fight their way into a second gateway to the demonic lands. But once there, Lotan, the son of the slain original nox demons, has different plans. He wants Bael dead, releasing the iron grip he has on both the human world and demon one--and Anya's the only one with the power to do it. But does she have the will?

The final book in the Demon Spring trilogy takes readers deeper into the demonic Underworld and into Anya's past.