Hell

Hell was a plane of existence, universe, or some sort of dimension that existed, embedded in the minds of species like Humans through religions like Christianity.

It had a firey geometry that gave the universe its name. The Scourge lived here and tortured the humans of their universe. (BFA: The Shadow of the Scourge)
 * Based on their statement, the Scourge either brought their vitims to Hell, or there may be humans living in Hell.

Jason Kane spent several years in Hell, described as predominately rock where tunnelling craft tunnelled their way between bubbles of places which weren't rock which would in theory be the equivalent of planets. This may have been the Infernal Regions, however, which is probably where the idea of Hell came from. (BFBS: The Infernal Nexus)