Valdemar by Mercedes Lackey

The long-awaited story of the founding of Valdemar comes to life in this 3rd book of a trilogy from a New York Times bestselling author and beloved fantasist.

The refugees from the Empire have established a thriving city called Haven with the help of the Tayledras and their allies. But the Tayledras have begun a slow withdrawal to the dangerous lands known as the Pelagirs, leaving the humans of Haven to find their own way.
But even with Haven settled, the lands around Haven are not without danger. Most of the danger comes in the form of magicians: magicians taking advantage of the abundant magical energy in the lands the Tayledras have cleansed; magicians who have no compunction about allying themselves with dark powers and enslaving magical beasts and the Elementals themselves.

Kordas, his family, and his people will need all the help they can get. But when a prayer to every god he has ever heard of brings Kordas a very specific and unexpected form of help, the new kingdom of Valdemar is set on a path like nothing else the world has ever seen.