'Diadems' in the Bible

Then another sign appeared in heaven: There was a great fiery red dragon having seven heads and 10 horns, and on his heads were seven diadems.

And I saw a beast coming up out of the sea. He had 10 horns and seven heads. On his horns were 10 diadems, and on his heads were blasphemous names.

and his eyes are as a flame of fire, and upon his head are many diadems -- having a name written that no one hath known, except himself,