'Diadems' in the Bible

Then another sign appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems.

And the dragon stood on the sand of the seashore.Then I saw a beast coming up out of the sea, having ten horns and seven heads, and on his horns were ten diadems, and on his heads were blasphemous names.

His eyes are a flame of fire, and on His head are many diadems; and He has a name written on Him which no one knows except Himself.