What happened when the sixth vial of God's wrath was poured out (Rev 16)?

The Euphrates River dried up, and frog-like unclean spirits came out of the mouths of a dragon, beast, and false prophet

The sixth angel poured out his vial upon the great river Euphrates; and the water thereof was dried up.

And I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet. Revelation 16:12-13