We are in the final part of the book of Revelation that unfolds The Day of Lord a climactic and final judgment from which God rescues his people. In Revelation 17 we have heard final judgment decreed for all evil. Revelation 18 continues that scene with the series of laments over the fall of Babylon.
Just as Daniel's friends faced the fiery furnace for not worshipping Nebuchadnezzar, Daniel himself is flung into the lions' den for not praying to the Persian king, Darius. Again we learn that God saves his righteous people and brings judgment on those who oppose him.