Valdemar: The Last Herald-Mage Series by Mercedes Lackey

Mage-Craft—Though Vanyel has been born with near-legendary abilities to work both Herald and Mage magic, he wants no part of such things. Nor does he seek a warrior's path, wishing instead to become a Bard. Yet such talent as his if left untrained may prove a menace not only to Vanyel but to others as well. So he is sent to be fostered with his aunt, Savil, one of the famed Herald-Mages of Valdemar.But, strong-willed and self-centered, Vanyel is a challenge which even Savil can not master alone... moreMage-Craft—Though Vanyel has been born with near-legendary abilities to work both Herald and Mage magic, he wants no part of such things. Nor does he seek a warrior's path, wishing instead to become a Bard. Yet such talent as his if left untrained may prove a menace not only to Vanyel but to others as well. So he is sent to be fostered with his aunt, Savil, one of the famed Herald-Mages of Valdemar.But, strong-willed and self-centered, Vanyel is a challenge which even Savil can not master alone. For soon he will become the focus of frightening forces, lending his raw magic to a spell that unleashes terrifying wyr-hunters on the land. And by the time Savil seeks the assistance of a Shin'a'in Adept, Vanyel's wild talent may have already grown beyond anyone's ability to contain, placing Vanyel, Savil, and Valdemar itself in desperate peril... less

The wild magic is taking its toll on the land, and even Vanyel, the most powerful Herald-Mage to ever walk the world, is almost at the end of his strength. But when his Companion, Yfandes, receives a call for help from neighboring Lineas, both Herald-Mage and Companion are drawn into a holocaust of dark magic that could be the end of them both.

The final chapter in Mercedes Lackey's spellbinding fantasy trilogy! The Herald-Mage, Vanyel, and his Companion, Yfandes, are alone responsible for saving the once-peaceful kingdom of Valdemar from the forces of a master who wields a dark, forbidding magic. And if either Vanyel or Yfandes falters, both Valdemar and its Herald-Mage must pay the ultimate price.

The Last Herald-Mage contains Magic's Pawn, Magic's Promise and Magic's Price.