The Sartious Mage by B. T. Narro
Jek Trayden is a Sartious Mage – famous for manipulating the heavy, green Sartious Energy with a skill that belies his age of just seventeen. But his power comes at a cost: terrible nightmares that attack both his mind and his body, leaving him with scars that he fears one may kill him.
The King has promised Jek a cure for the “darkness” that attacks him while he sleeps, if only he will perform a task. When the King reneges on his promise, Jek takes drastic action, kidnapping one of the royal princesses and fleeing the city in an attempt to persuade the King to keep his word. But far from solving his dilemma, Jek very soon realizes that his problems have only just begun… (More info)