Magic's Promise (The Last Herald-Mage Series, Book 2)

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.