Dragon-Ruler

The Dragon-Ruler, Dragon-King or Lôke-Kân' is one of the supposed Titles of the Leader of Sauron´s great eastern Host, the [Golden Army.

Speculations
Dragon King originally was one of the Names of the Nazgûl Khamûl.It is suggested that Khamûl played a central role in uniting the desparate Easterling Tribes and forging them into one single military force.It seems possible that Khamûl took the role of the Dragon-King while forming the eastern Army and passed the Title unto his mortal sucessors.Hûz III, Borthand or Tarôk, Zhamik, Amdûr and Vacros all may have been Dragon-Kings or at last high-ranking officers is the great eastern Army.