When children toiling in the darkest part of the Cedarbrook Mine found a shaft sunk deep into the earth - a shaft that could have been dug by no human hand - Parliament was quick to act. The blind, emaciated survivors of the First Expedition were hastily packed off to asylums and secluded estates in the country, but the notes and maps they carried home were endlessly poured over by Her Majesty's patient administrators. The discovery - a vast, sprawling cavern system, home to clusters of edible black fungus, accessible only from above - could not have been more perfectly suited to the Empire's needs. They decided to name the settlement Fort Providence.
The army jury-rigged a rope elevator. At its first use the rope snapped, sending a basket-load of convicts clattering down into the dark. Their mangled corpses were never found. The second load of settlers survived for months in near-darkness, on starvation rations dropped down from the surface, desperately trying to work out how to farm the fungus. Parliament intended the colony to be self-sufficient - they resented having to pay for it. It took several years for the convicts, working under military supervision, to hack out houses in the cavern walls and get the hang of subterranean agriculture. Only when they struck a vein of copper did the town really begin to grow.
Decades later, the colony of Miasma thrives. The earliest convicts worked off their seven-year sentences, obtained their tickets of leave, were granted land by the government and a fresh supply of felons to work it. Their children are dark-adapted cave urchins, raised on half-believed tales of the bright lands above. They're allowed to return to the surface but rarely wish to. The First Subterranean Regiment, nicknamed the Devil's Own, are a rum-swilling, unshaven, sadistic mob who enforce the Governor's laws with bayonet and manleather whip. Fort Providence, in its bottle-shaped cavern with its huge central guard-tower, has a church, a hospital, a newspaper. Convicts who violate its myriad laws are dragged off to the secondary hells - satellite colonies in the surrounding caves, established to terrorise and punish those felons who are recalcitrant or incorrigibly criminal by nature. They are all governed by their own sinister Wardens, and all awful. Some contain their own tertiary hells. Nobody knows how far it goes. You can get sent there just for looking at a soldier in a funny way.
Anyone can walk away from Miasma into the surrounding caves at any time. The Veins are so insanely dangerous that most people who do just die, or are returned by Volumefolk or wandering Olm in exchange for rewards. The colony, being supported by a surface state, is very rich by Veins standards. The Devil's Own employ a few Olm trackers on a semi-permanent basis. On the other hand, it's not unknown for a tribe of Veins natives to take an escaped convict in and teach them how to survive in the underworld. These lucky few become Veinrangers - preying on the colony's outskirts, raiding their fungus-farms, stealing a sonic pig or two and vanishing back into the darkness. The PCs begin as convicts in a chain gang, brutalised by a heartless overseer, on the verge of being flogged to death. Escape is their first challenge. Becoming a band of Veinrangers is the second. The campaign's final goal is to find a way back to the surface. The obvious way is the rope elevator in the central shaft above Fort Providence - it can only be operated from above, and gravity is the enemy.
- Mandatory silence, darkness, solitary confinement. Based on the Auburn System. Prisoners weave silk from ultraviolet caterpillars.
- Half-flooded tunnels too low for a man to stand. Prisoners shuck black pearls from cave-oysters and slowly forget how to walk upright.
- Opal mine. Prisoners keep a fraction of their finds, must use it to pay for food and lodging. Meant to teach virtues of industry. Lots of gambling.
- Slowly flooding cells with four convicts apiece. Heavy crank pumps the water out - one person must always be turning it.
- Farming unusually huge black fungi. Near a natural fission reactor - convicts are rapidly and grotesquely mutated.
- Cramped cages dangling above lakes of lava, their iron bars agonisingly hot. The guards drop food-scraps from above and the prisoners must catch them.
(this is all based on Robert Hughes' classic of Australian history, The Fatal Shore, which I have just read. also there's a joke here about Down Under but I can't figure out what it is. I might do more on the Hells later but also maybe not)