High-King

The title High-King means that this specific king rules other kings or queens. And in times long gone this title was given to any creature to rule thus, be it man, woman, dragon or whatever.

"Today the title is not really used only in that way. In the last few thousand years, countries have used the title to enhance their own, perceived importance, or have called rulers High-Kings or High-Queen when the subservient nobles are especially powerful or independent.

Also derivates of this title, like High-Duke have come about and it has become custom in some regions to include fürther, descriptive terms. So one can hear fanciful titles like "The High-Draconic-King of Sultrari".
Who is at best an uncivilized, illiterate, clansman ruling over a town on the shores of the Stout Sea."

From a lesson about titles and rulers