Not even the solipsist monsters of the Abyss can continue forever under conditions of ever-changing insanity; some ideas produce too great a gravity for even the the most fluid minds to escape. And so, like a body faced with cells that might mutate beyond restraint, the Abyss walled off the offending ideas in a cyst. The cyst endures in the astral nothingness, holding its dark enlightenment within. This is the Black Iron Prison.
The pull of the Black Iron Prison attracts others. Monsters of the Abyss convinced that something besides Self was real and that something was Punishment. But by whom? The Godhead who had appeared to have forsaken them or some new Godhead yet to come?
Fearful and paranoid, the monsters elaborated prisons around the original one like nested labyrinths. There they hid, and interrogated and punished themselves and any other souls that fell into their grasp.
Some might consider the multiverse's largest prison a place of Law, but there is little Law here. Rules are arbitrary and changeable. As are punishments. All the jailers operating under vague authority are just more prisoners. Those jailers, the prisoners with the longest sentences, are the fiends called deodands, this name being an an ancient term for an object which has caused a death and so is forfeit to God. If anyone knows why the fiends have this name it is the Baatezu, and like most secrets, they have classified the information.
The most common deodands are tall, emaciated, scabrous creatures with frog-like mouths. Their bare skins weep a tarry ichor from numerous injection sites. They're junkies and dealers; they mix the astral excreta of despair, callousness, and fear that oozes from the souls that fall into their hands with the bile of arthropods that make their homes in the prison’s substructure and inject it beneath their skin. The tarry substance--and a brief respite from their paranoia in a cold, sneering high--are the result. The tar is packaged and sold (to the prisoners to be smoked or injected) in exchange for pleasant memories or dreams or hopes--anything that defines the former self-hood of the soul. When not engaged in commerce, these tar deodands are the menials of the prison.
The the second most common variety are the color of a fresh bruise. Their limbs are swollen like blood sausages, and their tick-like bellies appear filled to near bursting, sloshing loathsomely as they waddle or fly drunkenly on ridiculously small wings. Their bloated faces are unpleasantly human-like and wear expressions of voluptuous satiety, complete with drool running from the corners of their mouths and down their double (or triple) chins. Always their skins appear to glisten as if oiled. They sweat even more when they eat, and they eat almost constantly. The eat when they are worried, and they are always worried. About informers or conspiracies. About a time when the tortures they apply to others might be applied to them.
The rarest of deodands have assumed the most authority. They often pass themselves off as wardens and are just as often found in solitary confinement. They sometimes watch and titter at the interrogations as they undergo torture themselves. They’re androgynous humanoids with bald heads and unfeminine faces, but pendulous breasts and high-pitched voices. Their pale, wrinkled skin seems ill-fitted to their bodies. They have a penchant for dressing in uniforms, the more elaborate the better. Sagging deodands, they are called.