Revelation 5:2

5:2 And I saw a powerful angel proclaiming in a loud voice: “Who is worthy to open the scroll and to break its seals?”

Revelation 9:14-15

9:14 saying to the sixth angel, the one holding the trumpet, “Set free the four angels who are bound at the great river Euphrates!” 9:15 Then the four angels who had been prepared for this hour, day, month, and year were set free to kill a third of humanity.