Then the sixth angel poured out his bowl on the great Euphrates River, and it dried up so that the kings from the east could march their armies toward the west without hindrance.
And I saw three evil spirits that looked like frogs leap from the mouths of the dragon, the beast, and the false prophet.
References for Revelation 16:13
They are demonic spirits who work miracles and go out to all the rulers of the world to gather them for battle against the Lord on that great judgment day of God the Almighty.
“Look, I will come as unexpectedly as a thief! Blessed are all who are watching for me, who keep their clothing ready so they will not have to walk around naked and ashamed.”
And the demonic spirits gathered all the rulers and their armies to a place with the Hebrew name .
References for Revelation 16:16