Path of the Dark by Jayne Castel

He’s been sent to assassinate a princess … but a beautiful sorceress threatens to ruin his plans.
Prince Elias of Anthor failed to kill the last surviving member of an overthrown royal family when he had the chance. Now his father wants him to finish the job. Traveling north under the guise of peace, Elias’s task is straightforward: start negotiations, get close to the princess, and end her life.
It’s straightforward until he meets a woman who will challenge him on every level.
Ryana is an enchanter who prefers singing in crowded taverns to following the rules of the Order she’s sworn to. A woman with a dark past, she’s trying to keep out of trouble when she meets Elias. He’s the son of a dictator, sent to negotiate peace with her king, and she distrusts him from the first—but she can’t deny the pull between them.
The Anthor prince represents everything she’s sworn to avoid. He’s dangerous, yet she can’t keep away from him.
Time is running out for Elias. But when it comes time to kill the princess, he finds himself faced with the most difficult decision of his life. Does he do his duty, listen to his conscience, or follow his heart?