Illuminate — C.L. Fennell

The world had changed after the war with demons, but it wasn't nearly as peaceful as people thought it'd be.

Max knew what it was like to be hated, he'd been hated since the day he was born. Prejudged because of a father he'd never met, labeled a demon and feared for reasons he'd never given. When a mission goes wrong and those he cares for are threatened, he's forced to make a choice- let them go or become the monster they'd feared he would be. In order to save them, he'd have to accept his power and show the world what it meant to be the son of Lucifer.

Misty knew first hand how evil and cruel the world could be. She'd spent the majority of her childhood being sold to people who loved nothing more than to cause pain in those they saw weaker, to abuse those who couldn't fight back. After the war with the demons, the world had changed, and Misty was no longer the little girl who needed protection. When someone threatens her adopted family, she's forced to release what she'd kept locked inside, even if it means destroying herself in the process.

Illuminate is a spin-off from the Soul Mark Series.In order to understand the backstory you might want to start there. Illuminate is book one of three, and follows Misty and Max.