Revelation 9:11-16

They have as king over them the angel of the bottomless pit. His name in Hebrew is Abaddon, and in Greek he is called Apollyon. The first woe has passed; behold, two woes are still to come. Then the sixth angel blew his trumpet, and I heard a voice from the four horns of the golden altar before God, saying to the sixth angel who had the trumpet, “Release the four angels who are bound at the great river Euphrates.” 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. The number of mounted troops was twice ten thousand times ten thousand; I heard their number.