Avernus is the hugely successful prison of the Magimundi, boasting not a single escape since it's founding. Prior to the end of the Magma Wars in 1830, Magimundi criminals were held in regional facilities in the Provinces, with no consistency of standards. But at the conclusion of the conflict at the Yellowstone Caldera, a young Marshal named Jack Hudson discovered a cave system protected by poisonous fumes and a host of Chupacabra who were taking refuge from the fighting. Through means he declined to explain, Hudson explored the cave system and located an underground lake over a magma vent that was the cause of the poisonous air. Hudson expanded the cave system into an underground prison complex he named Avernus where Magimundi prisoners would be guarded by Chupacabra. Regional jails and prisons were emptied, prisoners were escorted into Avernus, and Jack Hudson was paid a considerable sum of Leeuwendaalders by each Province.
Stripped of all personal effects, a prisoner is brought to the Avernus “foyer” by Marshals where they are handed over to the Chupacabra guards. In absolute darkness, the Chupacabra bodily carry the prisoner past the toxic fumes, and deposit them into the prison. While most persons sentenced to Avernus are serving a life sentence, those serving a finite term are deposited in the “foyer” the day their sentence ends. Sometimes as corpses, sometimes without any magical ability, but almost always as mere shadows of their former selves. Problematic mages sent to Avernus are rendered invisible and forgotten by the Magimundi; it’s nearly impossible to visit someone there, and those who do get the permissions can only stay for a short period of time before their health and sanity is harmed. The inmate population in Avernus continues to rise, with noticeable trends in the demographics of prisoners. Mages outnumber accredited Wizards, there are far fewer Unsoiled Heritage family members incarcerated, and prisoners who may have done what is functionally the same crime, but using a different type of spell or magical tradition find that they have widely varying sentences, ranging from a few months to life for breaking and entering, for example.
Avernus is continually under expansion, driving yet more Leeuwendaalders into the construction, magical wards and protections, and the training of more and more Chupacabra. The growth of Avernus has been a source of revenue for many companies formed solely to support the Avernus complex. A troubling trend for activists (but a highly profitable one for Magimundi business owners) is to use the inmates at Avernus as contracted labor for other companies or government functions. Foresight Enterprises, run by the Hayes family, uses inmates for some of its mining work, the Mishipeshu province sends low-skilled bureaucratic work to be done by prisoners, and Virginia Isle has many secret contracts with Avernus of unknown terms.
The Bureau of Conduct and Consequences operates out of Avernus Prison and employs a garrison of marshals specifically empowered to investigate crime and offenses in the Magimundi. Many justices are also in employ of the bureau, and are tasked with the determination of which offenses even qualify as a crime within the purview of the Magimundi.