When the horde of Undead Flying Insects swept over, the Demons that roamed this decaying grassland met their doom.
Ange Watson had chosen this location very astutely, as the Demons left here were nothing but lost dogs.
There was no semblance of order among Demons, so internal fighting was common.
Those Demons, defeated by their own kind and not yet devoured, would run off to some secluded and hostile places to lay low for a while.
This space, cloaked by the Chaos Black Sun, was vast, but finding a safe haven was not an easy task.
This putrid grassland was one such place, with rotting, foul-smelling soil and countless parasites. It just lacked any useful resources.
The Demons were too preoccupied with entering Space Gates to invade other worlds to care about this refuse area.
Thus, there weren't many Demons in the grassland, and those that were there were mostly weak and cowardly, quickly cleaned up by the Undead Worms.