Firefrost

She’s a huntress: Sol d’Hillerod is sent on a desperate mission through a treacherous winter pass. She carries with her the only hope of her village’s survival, and she will do whatever she must to keep her world from burning.
He’s a monster: Lieutenant Kelan Birke has spent his whole life fighting for his freedom and his soul. As his control slips, and the war rages on, he knows it won’t be long before he loses himself entirely to the fire that flows through his veins.
Sol and Kelan are enemies in an age-old war, forced to depend on each other to survive a perilous journey through the mountains. As fire melts the ice in Sol’s heart, she questions everything she’s been taught to believe, and Kelan becomes more desperate to fight the flames that consume him. Together they discover that their struggle will have repercussions for both sides of this burning war.
Firefrost_ in a prequel novel, which takes place before Flameskin, book one of The Flameskin Chronicles series. _