13 Then the sixth angel blew his trumpet, and I heard a voice from the four horns of the golden altar before God, 14 saying to the sixth angel who had the trumpet, “Release the four angels who are bound at the great river Euphrates.” 15 So the four angels, who had been prepared for the hour, the day, the month, and the year, were released to kill a third of mankind. 16 The number of mounted troops was twice ten thousand times ten thousand; I heard their number. 17 And this is how I saw the horses in my vision and those who rode them: they wore breastplates the color of fire and of sapphire and of sulfur, and the heads of the horses were like lions' heads, and fire and smoke and sulfur came out of their mouths. 18 By these three plagues a third of mankind was killed, by the fire and smoke and sulfur coming out of their mouths. 19 For the power of the horses is in their mouths and in their tails, for their tails are like serpents with heads, and by means of them they wound.

20 The rest of mankind, who were not killed by these plagues, did not repent of the works of their hands nor give up worshiping demons and idols of gold and silver and bronze and stone and wood, which cannot see or hear or walk, 21 nor did they repent of their murders or their sorceries or their sexual immorality or their thefts. (ESV)