Piranesum

The Eternal Prison

"Piranesum." It is a name spoken in whispers, darkly alluded to, striking a cold fear into even the most black-hearted souls. It is the Prison of the Gods. This grim realm of endless stone and metal is reserved for only two sorts of creatures - the victims of freak accidents, and those depraved souls so evil, so vile-hearted, that not even the grace of the gods can redeem them.

Ever-Growing Expanse

The Eternal Prison is the domain of Piranesi, the Delirious God. He works in a frenzy, struck with fever-dreams and hallucinations, and as he builds, the prison grows. Stone shears off from stone, mortar squeezes from in between the cracks of weathered brick, and iron bars surge from within the gaps of ancient archways, standing locked without a key. Infinite vistas stretch out in every direction, a monument to architecture slowly vanishing in the thin fog that permeates the escherian halls, impossibly large archways, and stairwells that take a lifetime to ascend.
Very rarely - once in a few years of travel - one might come upon a rare garden of lucidity, the result of Piranesi falling asleep at his work, or perhaps the random roll of chance resulting in a coherent structure. Sometimes, these structures even have soil. Even rarer still, one may stumble upon a literal garden - food, water, and shelter. These seldom stay private for long.

No Escape, No Hope

Once a soul enters Piranesum, it is never permitted to leave. All entrances to the prison are one-way, protected with a seal so immense in power that even the souls of its denizens are not permitted to escape to the afterlife. The damned inhabitants of the prison - Anima Sola, the metaphysical given form - are fond of thoughts of escape, of finding a fabled exit to the endless halls. There are, of course, no stories of such a thing ever being found.
Even if one of the damned souls of Piranesum found an exit... why would they return to tell the tale?

Type

Dimensional plane