and many lost souls.
"Whose hell is this?"
Hades receives souls from several worlds, including an Earthlike Terra. Demons are influenced by, and can visit, all of these worlds - and others. If hell has a culture, it is a mixture of all of these worlds' civilisations - or the ones that believe in a hell, that is.
People only go to hell after death if they believe in hell and believe that they are going to go there (or want to go there, or are sufficiently obsessed with it for some other reason).
Hades reacts to the fears and expectations of those trapped there. Since these are all different, no two souls experience the same 'reality'. People with similar perceptions tend to congregate, creating 'realler' shared pockets of 'reality'.
Demons can see these illusions and can interact with them, but are not constrained by them. It's a little like knowing the scenery is fake and being able to duck behind it (and sometimes manipulate it), only the scenery is 3D.
Interestingly, demons do not take any part in souls' torments unless the individual demon enjoys inflicting pain (or is attempting to help). Because demons can shapeshift, they can appear congruous with a soul's illusions.
It is possible for a soul in Hades to leave. Not many of them believe it.
Hades came into being as a result of belief - several cultures' beliefs - in a bad place that would take you after death, and that was inhabited by, or connected to, chaotic creatures who can take any shape they wish and understand the thoughts of people.
Hades was shaped and buffeted by this belief until, somewhere along the line, it became self-aware. It has more overall stability after this point, but don't be fooled by the concept of self-awareness - it does not communicate (although there's nothing to suggest it couldn't) and doesn't seem to have any desires or aims of its own.
It has a sibling realm, though differently constructed, called heaven.