The First Demon King is the God Emperor, a Wizard that had been born the son of a unnamed God and a Human, and rose to prominence as the worst Dark Wizard of his time roughly Seven Centuries before the birth of Zeref. He was defeated over One thousand years before the story, by a great Hero but due to his divinity, only his physical form was destroyed as he had created his own form of afterlife from where his soul resided and would return from every three hundred years to possess the Vessel that would become his Shintai.
During the time in between his resurrections, a Demon King is chosen to tend and rule his Empire from Stygia, the Empire's Capital. When the God Emperor walks among them once more and sits upon the throne, the Demon King continues to serve and run the Empire at his side as the Empire's Minister of State.
- With exception to the original holder of the title, the Demon King serves a similar role to Minister Yajeel of the Alvarez Empire.