Shield of Fire by Boone Brux (Bringer and the Bane, #1)

Protecting humans is the Bringers' duty. Sending demons to the Shadow World is their pleasure.
In one night, Ravyn's life plunges from barely tolerable to deadly. Forced to flee the only home she's known, she stumbles headlong into the clutches of Icarus, a powerful demon intent on stealing her powers. Unfortunately for him, she has no intention of cooperating.
When Rhys realizes the woman he's rescued from the Bane Demon is no mere human, his obligation as a Bringer dictates he protect and train her in the ways of his people. But he's unprepared for the intense desire he feels for the fiery Ravyn. To surrender to his need may mean her death.
As the Demon King's desire for ultimate power escalates, fathers are slated against sons, and foes are made allies. The Bane threat upon them, Rhys and Ravyn must quest to unite the last of the Bringers--and explore a passion too powerful to ignore.