Aerie: Book Four of the Dragon Jousters

In the fourth and final novel of Mercedes Lackey's Dragon Jousters series, Kiron, the man who had once been a dragon-boy called Vetch, has united the dragon riders and managed to rid their world of both war and magical domination. But are the evil Magi really gone for good? As Kiron tries to build a new civilization at the site of an abandoned cliff dweller's city, called Aerie, conflicts arise, and he soon realizes there is a vast conspiracy at work, which includes individuals who have infiltrated every walk of life-even his own family. Once the heads of the Magi, these conspirators are determined to regain their sinister control.