The Witch of Two Suns series

The shari'a people are an ancient race-a proud and gentle people, ruled by witches who harnessed the powers of the world for the benefit of all. When the seafaring Allemanii tribes came to their shores, the two races lived side by side for generations, staying apart but trading and learning from each other in peaceful harmony. But something went horribly awry and the shari'a people were suddenly and brutally slain by the settlers who had come to dominate the land. They feared the shari'a . . . and more important, the witches who led them and who held powers that the Allemanii could barely comprehend.