In Volume 30, the Encroachment was first brought to the surface. This involved the Archive formatting all realities, erasing every reality until nothing was left. Because for every choice, a different reality and dimension would be created, numerous realities would overlap another, replacing it entirely. If one dimension was bare, and was replaced by an ocean, then the people within that world would drown. Reality and Virtual Reality was mis-mashed together.
In the beginning, this corrosion was so advanced, that it has affected the entire Beltline, which in effect, was affecting Lower Town. Eventually, all space-times would start to collapse, completely becoming nonexistent.