Hell in Omnipotent Ascension is categorized as a multiverse with 7 layers belonging to the seven rulers of hell.
Each sphere of hell has infinite size with only the first sphere having a beginning and end, each sphere of hell continuously expands in size to accommodate the souls that get sent there every minute.
The first sphere is a finite 3D space with an infinite number of pocket dimensions, it has a realm only accessible to the ruler of that sphere and to those of higher ranks than him, with Mammon being the ruler of this sphere he has unlimited control over it and can do anything he wants with the space.
The othere spheres on the other hand are infinite 4D spaces which completely transcend each other with a higher sphere transcending the one below in space and time.
The seventh sphere of hell where Lucifer resides and rules over is a different case as it is a realm which has an infinite number of possibilities and realms within it, having different realities and different outcomes of judgement, the only single being in this sphere is Lucifer as he was the only Lucifer created by The One and cannot exist in more than one space yet he exists in all spaces at once as the omnipotent ruler of hell.