Spine of the dragon

Thousands of years ago the god Kur created the wreth, beautiful and powerful in magic. Then he commanded them to destroy Ossus, the dragon at the heart of the world, and disappeared telling them that only when the dragon was destroyed would he return. The wreth created a lesser race -- the humans -- as servants, slaves and soldiers. Millennia later the land is fertile again. Humans have survived; the wreth and Osus are tales of a legendary post.... until they ride out of the desert wasteland and demand the human return to service. -- adapted from jacket