The first emperor is said to have been given a profetic vision by Verity, showing him the place of everyone in life. This vision showed him that humans were closest to the divines, and as such should rule. All other races are to serve humans.
Long before the empire, magic was outlawed in the small country of Silicia, the homecountry the imperial family due to the corrupting effects. This has evolved to the use of controllers in the empire. Many see it as a civil duty to report magic users to the authorities.