Crowley's Pit

Crowley's Pit, named after the devil Crowley, the former devil who worked under Lord Asmodeus, is a prison that hosts most of the Underworld's criminals, hosting the criminals who are deemed to weak or inferior to be sent to the Cocytus while hosting criminals of every kind, from murderers to thieves. The prison is first referenced in Life 8, as Marcus Keller was sent there after being defeated by Dark Ichiro and captured by Gray Dantalion when he attempted to escape Kuoh Town. In Dragons of the Apocalypse, it is referenced in the Prologue that most of the stray devils or creatures that the Rebekah group captures are sent to this prison and that the prison is maintained by the combined efforts of Nero Belphegor and Caesar Lucifer, the latter of the two being the one who condemns most of the prisons to this area.

Exterior
The exterior of the building is rather dim, it is surrounded by giant thick red trees which produce special devil fruit (with inmates being given the job of farming and picking the fruit). Behind the trees is a giant metallic gate created by Ajuka Astaroth in order to drain the demonic energy of the prisoners and disables their ability dispatch their wings for flight, almost making them human in a way. The prison is shaped like a giant brick castle that gives off a eerie and horrible aura according to Rebekah.

Interior
The hallways of the building are shown to emit a purple light, the original sky color of the Underworld, and inside is a giant stairway, each floor leading to rows and rows of rooms, while the lowest floor holds the dining area, kitchen, and rec room. Despite the history of the prison, due to it's remodeling the rooms look relatively nice, possessing a bunk bed, with a simple long brown desk with two chair.

Heavenly Dragon Kings' Rebirth
Crowley's Pit was originally created by the devil Crowley to host as a prison for POW (Prisoners of War) and was the main hunting ground of the Original Alastor who used the prison to torture a majority of the inmates, both physically and mentally, being known for depriving of food, using holy objects and blasting prayers through the speakers to inflict the angels, who felt abandoned by Heaven, to the fallen angels who felt malice towards their God, and to cause physical harm to the devils. As a result, even though his actions were centuries ago, the Alastor name still carries a lot of hatred and malice.

After the conclusion of the Devil Civil War, Sirzechs reformed the prison to be more humane and due to the stalemate of the Great War released all the angels and fallen angels that were still in captivity. Using his new role as the ruler of domestic affairs, he has since then turned the prison to a ordinary prison to host devils, humans, and other supernatural creatures who commit sins against other devils and humans. According to Ichiro, Amelia got two servants from this prison, who had both been sent there due to stealing from families, stating that she played on their negative feelings towards the 72 pillars to get their allegiance. In Life 8, Marcus Keller is sent here, due to not being deemed dangerous enough for the Cocytus, the exact extent of his sentence is never revealed but it is implied by Gray jokingly that he won't be released until the day Issei finally becomes a harem king.

Dragons of the Apocalypse
In Dragon of the Apocalypse, the history of the prison is quite difference, as Crowley Lucifuge instead used the prison as a mental institution, however this was merely a front in order for his experimentation with the creation of Super Devils by using numerous devils who were of lower status as victims. According to Arie Mammon, hundreds of devils were tortured in the place and that it wasn't until the Devil Civil War was coming to a close as Nicholas Satan was marching to the place with devil troops to completely put a end to the prison. However it is implied by Nicholas that he never got the chance to officially put a end to him as he had decided to put himself to bed before his arrival.

In order to save on money, instead of simply destroying the place Arie Mammon decided to have it reconstructed as a prison due to it being relatively distant from the capital but close enough for Caesar Lucifer and Nero Belphegor to be able to regularly visit. Due to Rebekah Orias's work under Arie Mammon, they regularly capture criminals and have them sent to the Pit.