(The previous passage should have been Rev. 16:1-21.)
In Rev. 17:1-18 the 7th angel showed John the punishment of the "great prostitute" or "Babylon the Great" (cf. Jer. 50-51, esp. 51:13, and Isa. 23, esp. v.3), drunk with the blood of the Christian saints (cf. Matt. 23:29-36, 1Kings 19:10, 2Chron. 24:22, Jer. 2:30), the great city who rules over the earth. The beast upon which she road was described as he who "once was, now is not, and yet will come". The beast's seven heads are seven hills and kings, five of whom have fallen, one who is, and one who has not yet come.
Although until this point in Revelation the great city seemed to refer to Jerusalem (cf. Rev. 11:8 & 14:8), reference to many waters, seven hills and ruling over the earth indicates awareness that Jerusalem has fallen to Rome, and the world's spiritual locus (around which the world's history of beliefs revolved) has been replaced by the political power. Thus, "kings" may refer to Roman emperors, "five have fallen" may refer to the first five (Julius through Claudius), the one "who is" to Nero, and the one who will "remain for a little while" to Galba (who reigned about six months).
The beast himself is an 8th king (probably Apollyon/Abaddon, the Destroyer from the Abyss in Rev. 9:11), and the beast's ten horns are kings who will rule with the beast and make war against the Lamb until defeated by Him and his faithful followers. The waters where the prostitute sits represent the world's nations and peoples, so the 8th king may refer to an eventual emperor of the entire earth including ten kingdoms. The beast and horns will also ruin the prostitute (anti-Christian Jews?, cf. Rom. 11:25-32) in order to rule until God's words are fulfilled (Rom. 11:33-36, 1Cor. 15:20-28).
In Rev. 17:1-18 the 7th angel showed John the punishment of the "great prostitute" or "Babylon the Great" (cf. Jer. 50-51, esp. 51:13, and Isa. 23, esp. v.3), drunk with the blood of the Christian saints (cf. Matt. 23:29-36, 1Kings 19:10, 2Chron. 24:22, Jer. 2:30), the great city who rules over the earth. The beast upon which she road was described as he who "once was, now is not, and yet will come". The beast's seven heads are seven hills and kings, five of whom have fallen, one who is, and one who has not yet come.
Although until this point in Revelation the great city seemed to refer to Jerusalem (cf. Rev. 11:8 & 14:8), reference to many waters, seven hills and ruling over the earth indicates awareness that Jerusalem has fallen to Rome, and the world's spiritual locus (around which the world's history of beliefs revolved) has been replaced by the political power. Thus, "kings" may refer to Roman emperors, "five have fallen" may refer to the first five (Julius through Claudius), the one "who is" to Nero, and the one who will "remain for a little while" to Galba (who reigned about six months).
The beast himself is an 8th king (probably Apollyon/Abaddon, the Destroyer from the Abyss in Rev. 9:11), and the beast's ten horns are kings who will rule with the beast and make war against the Lamb until defeated by Him and his faithful followers. The waters where the prostitute sits represent the world's nations and peoples, so the 8th king may refer to an eventual emperor of the entire earth including ten kingdoms. The beast and horns will also ruin the prostitute (anti-Christian Jews?, cf. Rom. 11:25-32) in order to rule until God's words are fulfilled (Rom. 11:33-36, 1Cor. 15:20-28).