Revelation 16:12
Then the sixth angel emptied his bowl upon the great river Euphrates; and the water in the river was dried up, so that the road for the Kings of the East might be made ready.
Revelation 9:14
It spoke to the sixth angel--the angel with the trumpet--and said 'Let loose the four angels that are in chains at the great river Euphrates.'
Revelation 7:2
And, in the east, I saw another angel, ascending, holding the seal of the Living God; and he cried in a loud voice to the four angels, to whom there had been given power to harm the earth and the sea--
Revelation 11:14
The second Woe has passed; and there is a third Woe soon to follow!
Revelation 17:15
And the angel said to me-- 'The waters that you saw, where the Harlot is seated, are throngs of people and men of all nations and languages.