Hell.
That's the name given by the mortal beings to the demonic plane, the place where the demonic race reside.
In truth, it's real name is not known, as like with everything else when it comes to demons, the real name is a world of power. So it's a secret well kept by its inhabitants.
Contrary to what most people think, Hell is not a disorganized place where chaos reign. To be honest, it's probably one of the better-organized places of the entire multiverse, if not the best.
It's divided into floors, with the bottom one being the most important. It's called the factory, and it's the pulsating black heart of the whole demon race. It's the place where demons are born, the place where the souls of evil people are tainted by the dark energies of the abyss and forged into the vilest creatures the universe has ever conceived.
Above it are situated the training yards, where the newly born demons are trained in the skills they'll need to survive, from torture to the best way to cause a genocide.
Above the training yards, on the second floor, there is Inferium City, the sprawling city where most of the demonic race members live. It's divided into three areas, everyone governed by one of the Demonic Sovereign.
It's in one of the poorer areas of the part of the city governed by the Succubi Queen that Gold's Shop of Horrors is located. Who is Gold? Nobody important, only a [Merchant].
A [Merchant] who's never been on the mortal plane and never hoped he'll be. After all, the only way for a demon to leave this home\cage was through a summoning circle and the mortals, while stupid, are not stupid enough to summon a type of demon specialized in deception and assassination.
But it seems he was wrong, as a summoning circle appeared under its feet while he was dusting one of the shop shelves. Maybe the mortals are really the epitome of stupidity, after all.