The Fire Lord’s Lover by Kathryne Kennedy

In a magical land ruled by ruthless Elven lords, the Fire Lord’s son, Dominic Raikes, plays a deadly game to conceal his growing might from his malevolent father—until his arranged bride awakens in him passions he thought he had buried forever.

Lady Cassandra has been raised in outward purity and innocence, while secretly being trained as an assassin. Her mission is to bring down the Elven Lord and his champion son. But when she gets to court, she discovers that nothing is what it seems, least of all the man she married.

But beneath the gilded castles lies an unspeakable evil, greater than either Dominic or Cassandra had ever fathomed, and without each other they may not survive.