Revelation 16:10

And the fifth angel poured out his vial upon the seat of
the beast
The beast is the same with that in ( Revelation 13:1 Revelation 13:11 ) and which again shows that to be one and the same: the seat or throne of the beast is Rome, which, when the empire was Pagan, was the seat of Satan, or the dragon, ( Revelation 2:13 ) and when the beast or antichrist was risen, the dragon gave this seat, as well as his authority to him, ( Revelation 13:2 ) and is that city which is so often called, in this book, the great city, and is manifestly pointed out by its seven mountains, on which the city of Rome stood, ( Revelation 17:9 ) and the pouring out of this vial upon it denotes the destruction of it, when it will be burnt down, and become desolate, an habitation of devils, of every foul spirit, and hateful bird, ( Revelation 18:2 Revelation 18:9 ) and this corresponds with the fifth trumpet; for as that brings in the rise of antichrist, both eastern and western, who rose much about the same time, so this vial affects him particularly; the western antichrist, his seat and kingdom. Mr. Daubuz refers this plague to the expulsion of the western and eastern emperors from their capital cities, Rome and Constantinople, and to the mischiefs caused by the antipopes in the west, and to the quarrels and schism in the Greek churches in the fourteenth century.

And his kingdom was full of darkness;
not only of the darkness of false doctrine and superstition, for so it was always, being filled with the smoke of the bottomless pit; nor only of judicial blindness and darkness, which the subjects of the antichristian state are given up unto; but rather of a discovery of all this, with all their hidden works of darkness, which will now be brought to light; though it seems chiefly to design the great affliction and distress the antichristian state will be in at this time, which darkness sometimes signifies; see ( Isaiah 9:1 Isaiah 9:2 ) ( Jeremiah 13:16 ) ( Amos 5:18 ) it having lost its sun, the pope, under the preceding vial, and its seat, the city of Rome, under this: the sense is, that it will be greatly obscured in its glory and magnificence, in its traffic and riches, ( Revelation 18:11-19 ) its power and authority will be greatly diminished, and it will be had in contempt by the princes of the earth; though it will not as yet be utterly destroyed, for its utter destruction is reserved for the seventh and last vial. The allusion is to the plague of darkness in Egypt, ( Exodus 10:21-23 ) . And they gnawed their tongues for pain; these are the men of the antichristian party, the subjects of the antichristian kingdom, now become full of darkness, the worshippers of the beast, and his image; these will gnaw their tongues, which expresses their inward anguish and distress, their anger, wrath, and fury, their being filled with revenge, and yet in an incapacity to execute it, and will even be afraid to express it; and therefore will bite their tongues in madness; and this for pain, for the pain of their mind, at the sad and low estate of the antichristian kingdom.