Due to the various law energies being drawn into the area to balance things out, this dimension's ambient energy concentration was off the charts.
Spatial law energy was one of those drawn in with the highest concentrations, to contain and prevent the destruction law energy from wreaking havoc on the continent's tectonic plates, and a mutation occurred, creating the dimension where the EREs were now.
The minimum requirement to exist there was the Legendary Realm. If an Epic was to go there, they'd feel like they were short on breath, or might even choke to death due to the law energy density.
As for the dimeson's walls, they were 'Spatial Destruction' infused; so, if you tried a forceful break-in, the destruction law energy would rebound on you and your soul.
