Steel and Shadows

An assassin stowing away on the King and Queen's ship foils a pirate raid and gains their trust; they witness his powers, and ask him to teach Elsa. Shortly thereafter, a storm wrecks the ship leaving him with only a letter from the King and Queen, his honor, and his conscience. He heads to Arendelle to start a new life. What will happen? His past certainly isn't in the past now...