The Spectral Realm is an area of the outsides of the universe, depicting the spacetime in the universe as a large course of landscapes, seas of miasma & forms of universal lava. The Realm has been syphoned from twice by the greatest monsters of the universe itself, all of which have been locked up in the magical towers of Thunder Prison.
The Realm can be accessed by spectral portals that open & can be found in holes of the universe. It is said that evil creatures are locked in the prison of the Realm, they say Zathura, the black hole, has been the prison, it's possible an entrance has been there & got sucked into the hole or the entrance is Zathura itself.
Thunder Prison are the magical prison towers that monsters have been locked in. Erwin, Electrospider & the Atomic Electrosphere have been locked in the prison for thousands of years. It is located on the farthest edges of the Realm.
Scraps of spectral junk & possibly things black holes take in, end up all disfigured & are sent to the junkyard of the Realm, located on the farthest ends, all the way across the Realm from Thunder Prison.