As the sixth trumpet sounds in the Apocalypse, Saint John, seen in the right margin, hears a voice from the golden altar. The illuminator identified the voice as the Lord's by including the bottom of a mandorla with the Lord's feet resting on an orb. The voice tells the angel with the trumpet to release the four angels who had been bound in the river Euphrates. In the miniature, these four avenging angels rise from the river with their weapons, ready to fulfill their mission of killing a third of the people on earth.