Then the third angel poured out his bowl on the rivers and springs, and they became blood.
And I heard the angel who had authority over all water saying, “You are just, O Holy One, who is and who always was, because you have sent these judgments.
Since they shed the blood of your holy people and your prophets, you have given them blood to drink. It is their just reward.”
And I heard a voice from the altar, saying, “Yes, O Lord God, the Almighty, your judgments are true and just.”
References for Revelation 16:7
Then the fourth angel poured out his bowl on the sun, causing it to scorch everyone with its fire.
Everyone was burned by this blast of heat, and they cursed the name of God, who had control over all these plagues. They did not repent of their sins and turn to God and give him glory.
Then the fifth angel poured out his bowl on the throne of the beast, and his kingdom was plunged into darkness. His subjects ground their teeth in anguish,
References for Revelation 16:10
and they cursed the God of heaven for their pains and sores. But they did not repent of their evil deeds and turn to God.
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.