Oath Sworn (Wolf's Oath #1) by Meg MacDonald

SPFBO6

One man’s oath. One boy’s sacred duty. One enemy bent on their destruction. Soldier and statesman, Aralt syr Tremayne has finally laid to rest the ghosts of his past. He could no more have prevented the death of the Kavistra’s sons than the death of his own brother. Now, the grave has given one of them up. Aralt’s world is thrown into tumult when Lian Kynsei, last of a soul-touched clan and scion of a religious dynasty, returns and Aralt is oath sworn to protect the boy’s interests. But Lian is also a traumatized boy whose secrets rival Aralt’s own. And neither of them are telling the truth. Oath Sworn begins the Wolf's Oath trilogy, a gothic gaslamp fantasy filled with unforgettable characters and a richly-drawn world where skyships sail above tidal extremes, and crystal swords are tuned to their owner’s souls. Follow this riveting adventure as one man is forced to choose between duty and his lust for revenge.