The Raging Fires (Merlin Saga Series #3)

Wings of Fire, the sleeping dragon, has awakened, threatening all of Fincayra. Only Merlin, whose magical powers are new and untested, can stop him. But before he can face the dragon's fires, Merlin needs to face other fires, including those within himself. Most importantly, he must discover the power—as well as the source—of his own magic.