Revelation 16:14-17

for they are spirits of demons, working signs; which go forth unto the kings of the whole world, to gather them together unto the war of the great day of God, the Almighty. (Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame.) And they gathered them together into the place which is called in Hebrew Har-Magedon. And the seventh poured out his bowl upon the air; and there came forth a great voice out of the temple, from the throne, saying, It is done