During a war between legions of the undead and the Council of Twisted, a vast track of the main city was forcibly removed and banished to a neighboring reality. As this area was populated those who found themselves removed with it began to build outwards in this harsh environment which began to be known as Hell.
Unified by a Council created by Señior Diablo, the outcast citizens managed to force back the undead and push the boundaries of that settlement into a full city. Since taking control of Twisted's Council, Diablo has been bringing those innocent souls back to Twisted and has actively sought to help them acclimate back into their old lives. The current state of "Hell" is unknown at this time.
Layers of Hell
The top-most layer of Hell is known as the Endless Plains. The inspiration for this layer comes from the pages of the Johnny the Homicidal Maniac, the comic where both Diablo and Johnny C. originate. The Endless Plains are literally an endless wasteland where the only distinguishing feature aside from some random jagged rocks is a giant eye which hovers ominously in the sky. The damned in this layer of Hell are obsessed with the idea of building cities under the gaze of that eye, making them feel important and accomplished. But as the eye randomly moves, so do the souls in the cities - choosing to create new cities rather than stay and maintain the one they're in. Because of this, this layer of Hell is littered with these abandoned cities in various states of disrepair.
Separated from the Endless Plains by a region of seemingly endless nothing, and connected by ancient scaffolding twisting downwards through the darkness between them, the Wastes are home to the demonic population of Hell. There grand cities like the city of Dis are built and seeing the damned being tortured or mutilated are commonplace. In fact it's in the city of Dis that judgements are decided for the souls who lived sinful lives and deserve some sort of eternal punishment - assuming they aren't recruited first of course. The Spire which houses Hell's Council's chambers can be found in this layer of Hell as well.
Continuing the journey downwards eventually brings one to the chaotic Heart of Destruction. There the normal perception of gravity is inverted as the streets and temples to various deities and Council Members are built on the inside of a spherical chamber in which the center beats a giant bloody heart, or a screaming skull, or a banana. The actual Heart of Destruction is chaotic, as mentioned before, and will change it's shape randomly without rhyme or reason. This is considered a highly spiritual area and all damned souls pass through here eventually.
Deep below all of the known regions of Twisted's Hell are a dense network of passages known as the Labyrinth. These passages, carved by the very dead who were originally enslaved there, are guarded by the Hell Priest and his Cenobites - Hell's version of TASK where membership is eternal. It is a place where pain and pleasure are carried hand in hand and anyone unfortunate enough to find their way there are never allowed to leave. Inspired by Clive Barker's Hellraiser, the Labyrinth is the only thing keeping the slumbering Leviathan below from waking up and destroying the Hells above it, and likely the rest of existence afterwards...
Many people have come to believe that Hell is more than just a name. It is a world similar to Twisted that actually connects and combines the various Hells of the multiverse into a singular realm populated by demons and the undead. Evidence of this exists in the form of the The Waiting Room where no specification exists between the afterlife and the realm where those banished from Twisted resided. While we're assured that this isn't the case and that this 'Hell' realm is just a colorful nickname; descriptions of demon cities, torture, and a massive underground labyrinth have been spoken of in hushed tones by those 'innocents' which Diablo has freed. Infact, looking up members of the Hell Council in the kiosk database reveal that-
Note: THIS POST HAS BEEN REDACTED.