That's quite the claim, doma. There are a number of dragons and serpents out there in mythology and heraldry. But if I remember correctly, in the Old Testament, the serpent was a baddy.
In the early history of kingship, it was fairly common for kings to claim to be Gods themselves eg Pharaohs and Roman emperors. The kings of Israel had their own special God of the people, of course.
In the Christian era, the role turned sacral. The king became a kind of uber-priest with special powers - touching his robe was meant to help with diseases, these kinds of things: but these powers were always derived from a Christian God. Meanwhile, the popes also claimed special powers of intercession with God and pretended they derived these from St Peter and from the Roman emperor. The two sets of powers ended up competing with one another, which crystallised in the investiture controversy. No talk of dragons and serpents that I can recall, other than for heraldic purposes.
Are there any dragons in the Koran upon which a caliph can rest his feet?
Not that I remember. The Moslems appeal to Allah and to his prophet. Neither is a dragon.