Rev 16:12-21

ARMAGEDDON
This is the return of Christ (hinted in verse 15), and the final great battle that ends man’s existence.
12 The sixth poured out his bowl on the great river, the Euphrates. Its water was dried up, that the way might be made ready for the kings that come from the sunrise.
Rev 16:12 (Sixth Bowl)
the kings from the east – we assume that since the true gospel was restored in the east, that those kings will battle with the king of the north, see also Dan 11:44.
13 I saw coming out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet, three unclean spirits, something like frogs; 
Rev 16:13
three unclean spirits – the kingdom of heaven was cleansed in the fifth bowl of wrath, and the saints were united in the truth. The Prayer of Jesus Christ for the unity of the saints has already been fulfilled. But as we read in Rev 20:7, Satan will be freed and deceive the world one more time, with demons who perform signs.

from the mouth of the dragon…the beast…and the false prophet – this is the deception of Satan described in Rev 9, that comes from the mouth of locusts.
14 for they are spirits of demons, performing signs; which go forth to the kings of the whole world, to gather them together for the war of the great day of God, the Almighty.
Rev 16:14
gather them together for the great day of God, the Almighty – this is the great day of His wrath, mentioned in Rev 6:17, Rev 9:15.
15 “Behold, I come like a thief. Blessed is he who watches, and keeps his clothes, so that he doesn’t walk naked, and they see his shame.” 
Rev 16:15
Behold, I am coming like a thief – at any moment now Christ will return to take His chosen ones home. The great day is a battle against Israel, which will be completely saved, as we studied in Rev 7. The King of the North, Gog, will come against Israel. We are just waiting for Christ to take His chosen ones out, as it were, passing through the Red Sea, described as the Mount of Olives in Zech 14:5. And “all the nations will weep and mourn” (Rev 1:7).

Blessed is the one who stays awake –  the final encouragement of Christ is to keep oneself ready for this moment. Do not be deceived, along with the world, by the final lying signs and wonders.
16 He gathered them together into the place which is called in Hebrew, “Har-magedon.” 
Rev 16:16
Har-Magedon – Armageddon is the Greek form of Megiddo. This is the Megiddo, mentioned in Zech 12:11, “in that Day (the Day of the LORD), there shall be a great mourning in Jerusalem, like the mourning at Hadad Rimmon in the plain of Megiddo.” The repentance of “the inhabitants of Jerusalem” is the last event that precedes the return of Christ. The meaning of “and they shall be together to the place called in Hebrew “Armageddon,” could refer to the place that the nations gather. But the more likely meaning is that the nations gather together, when the “inhabitants of Jerusalem” repent.
17 The seventh poured out his bowl into the air. A loud voice came forth out of the temple, from the throne, saying, “It is done!” 
Rev 16:17
upon the air – the speech is “upon the air.”

a loud voice saying “it is done” –  the voice of the Spirit of Christ, speaking for the invisible God, see Rev 21:6, “It is done.”
18 There were lightnings, sounds, and thunders; and there was a great earthquake, such as was not since there were men on the earth, so great an earthquake, so mighty. 
Rev 16:18
a great earthquake  – a great war, see also Rev 11:13 which described the war that killed “a tenth of the City” who died in the Reformation and ongoing religious wars. This “great earthquake” destroys a third of mankind as mentioned in Rev 9:15.
19 The great city was divided into three parts, and the cities of the nations fell. Babylon the great was remembered in the sight of God, to give to her the cup of the wine of the fierceness of his wrath. 
Rev 16:19
the great City was split into three parts – Mystery Babylon is compared to the idolatrous Israel, who God judged in Ezek 5:2: “you shall burn with fire 1/3 in the midst of the city, when the days of seige are finished; then you shall take 1/3 and strike it around with the sword, and 1/3 you shall scatter to the wind…”
20 Every island fled away, and the mountains were not found.
Rev 16:20
every island fled way… – possibly the effects of Nuclear blasts.
21 Great hailstones, about the weight of a talent, came down out of the sky on men. Men blasphemed God because of the plague of the hail, for the plague of it is exceeding great.
Rev 16:21
hailstones, about one hundred pounds each – the hailstones of Rev 8:7 were metaphorical of “sores” on those who worshiped the image of the beast and received his mark. These may be missiles that appear as hailstones. The great hailstones are metaphorical of the absolute destruction of Babylon. The great earthquake and hailstones are also described in Ezek 38:18-23. God used large hailstones to destroy Israel’s enemies in Josh 10:11.