A powerful angel descended from heaven and announced that the cities represented by Babylon were about to be completely destroyed because of their immorality and idolatry.

Revelation 18:1-3

18 After this, in the vision I saw another angel, who had great authority, coming down from heaven. The earth became bright because he was shining so intensely/brightly. 2 He shouted with a very loud voice, “God is about to completely destroy [DOU] all the very evil cities (OR, the very evil city) that Babylon represents. As a result, all kinds of evil spirits [DOU] will live there, and all kinds of foul and detestable [DOU] birds will live there. 3 God will destroy those cities because their rulers have persuaded the people of [MTY] all nations to act very immorally and idolatrously with the people of [MET] those cities, just like a prostitute persuades men to drink strong wine and then commit fornication with her. The rulers of the earth have also acted immorally and idolatrously with the people of [MTY] those cities. The merchants of the earth have become rich because the people of those cities strongly desired and bought from the merchants many ◄luxuries/expensive things►.”