Seven Sides Away

Our world is over, with overlapping cities, chaotic history, the "black mud" that eats people, and the "entropy vortex" that keeps appearing like ghosts and then disappears, leaving a mess behind. The edifice of science collapsed, and the broken world was forcibly pieced together by a strange force. In such a strange end of the world, people can't help but ask, what is the end of this world?