Acolyte by Pengrey

He who has power will surely abuse it, and those who have none will fight to take it for themselves. Callum is an orphan and a thief in a city where magic is a dirty word. He dreams of leaving Aljana to become a master of the arcane, to leave behind a life of abuse and destitution. An opportunity for escape presents itself in the form of a visiting wizard named Willow, who comes on the invitation of the Padishah Sultan himself. With a single misstep, Callum and Willow will find themselves bound in a destiny that traces itself back one hundred thousand years, to the bedchamber of a dying king and his Starlight Queen.