The Megadungeon That is a Train

I've been thinking about different ideas for a dungeon setting. Specifically an interminable, unfathomable megadungeon that defies the normal rules of the world. Such places seem to be the perfect setting for an adventure story that would be told, but scarce believed, around a campfire, or at a bar strewn with empty glasses.

Railsea cover from the art of Les Edwards

For some reason I thought about a train. I'm sure it's not original, and has probably been done before somewhere, but there's something about the idea that is at least interesting. Trains can be somewhat demonic and unpleasant things at the best of times. The process of a long train journey can be tiring endeavour, and that's when things aren't specifically trying to kill you or sabotage your trip. It might seem that way, but it is indifference only.

Things about trains that can be bad include- 

Waiting for a train you think might never turn up.

Finding out you have the wrong ticket and have to pay a penalty fare.

The toilets.

The food on the trolley.

Drunken passengers.

Sober passengers.

Screaming babies.

Motion sickness.

Hearing 'the train approaching platform 1 will not stop here. Please stand back' and then a train screams past at 500 miles an hour going 'SHOOM-SHOOM-SHOOM-SHOOM-SHOOM!!!!' for a whole awful minute. One of the things that truly terrifies me.

But anyway, this dungeon. Possibly inspired by my own fears and prejudices.

A train of blackened and rusted iron, in perpetual motion that stretches for miles and miles, carriages as big as cathedrals, seething and coursing through the different dimensions, planes, and planets of the universe like the river styx. No windows- an oppressive, coffin-like edifice which feels like it could be in the deepest reaches of some mechanical hell. Always in motion, always a roaring cacophony of machinery. The tacking, thrumming noise driving into your skull forever, the swaying and shuddering motion making its way unbidden into your very bones, and the howling train's whistle heralding its approach, echoing through the dimensions of the multiverse like a banshee. I'm imagining the fantasy elements somewhere along the lines of China Miéville's Iron Council or Railsea. That is to say weird, overwrought, and excessively rich and bizarre, but all the more brilliant because of it. A train in perpetual motion, older than anyone knows, being forever patched and repaired by engineers that spend their entire lives aboard the locomotive. A caste of creatures dedicated to keeping the train moving, keeping its masters happy- pursuing agendas that they cannot possibly understand, and probably wouldn't want to if they could.

But why are the adventurers aboard the train? Perhaps they happened to see it in the wilderness, making its inexorable way across a blasted landscape. One of the rare occasions when it bursts into the physical plane- exploding out of a mountainside like dynamite from the walls of a quarry, or shooting from the mouth of an ancient cave, or roaring and steaming out of the ocean like some unholy, hulking iron cetacean, only to vanish again without a trace

Perhaps they woke with a pounding headache, their alcohol-pickled brains barely remembering the night before. They boarded the train in a moment of drunken delirium.

Or perhaps they needed to barter for passage onto the train- to reach another plane or chasing the rumour of a great artifact currently in transit. There would be those in the know. Shady dealers that know where the train might be passing through next. Occult diviners of the locomotion, seers of the engine.  The oil they use is from the train itself- black and viscous. They take it like a psychoactive drug and peer through veils of steam, selling their knowledge to the highest bidder. The train could next come coursing through an urban sewer, an immense subterranean waterway, or screaming through an abandoned station on the edge of town.

And once aboard, where do they go? What do they do? It seems hopeless. The train is miles long and each carriage the size of the greatest edifices of human-kind's architectural imaginings. Is it possible to tell which way the train is going? Do they want to go forwards to the driver's carriage, or back to the end of the train? Does the train even have an end? Perhaps it stretches back into an abyssal mass of machinery and fire, steel and grease. No one knows. These questions may never be answered. The characters must face the interminable decision- stay where they are and wait for the train to come to a halt, or forge on in either direction.

P.s. I realize that this could sound like an impossibly awful and linear dungeon. It is literally a big line of rooms, however you might spin it. But a train this big would have other ways in which to traverse each carriage. Auxiliary corridors and emergency transit corridors, more walkways running under the main floor of each carriage, and walkways hanging high above it. Similarly, each carriage could be so big it could house multiple types of ... carriage biome? Whatever. My point is, I'm trying to convince myself that is't not an entirely boring and linear adventure. I think the main appeal is that it is modular. The train can be filled with anything, and there is no restriction on the order in which things are encountered, except perhaps the locomotive itself at the front, if they ever get that far.

By Rivende on Flikr

What do they find in the next carriage?

As they make their way along the train, the heavy doors and flimsy corridors that connect the carriages reveal ever stranger sights and sounds. Roll and find out. I feel like I've gone a bit mad on the exhaustive description of this list, but hopefully you get the idea.

• A freight carriage: Crates, boxes, murky jars. Hundreds upon hundreds of them stacked up into the soaring darkness of the train. Names, routes and destinations scrawled upon them in a myriad of different languages, they contain goods from countless places, on their way to countless more. Huge iron containers graven with unrecognised sigils, immense wooden boxes with warnings and official documentation nailed to them. A giant glass tank, filled with viscous brown liquid, holds a faint and indistinct shape twisting and turning in its depths. Oddly alluring smells come from terracotta urns big enough to hold a person, stoppered with black wax and stamped with seals proclaiming their ownership. There could be untold wealth in these containers, if only one could leave the train and find somewhere to spend it. Some containers have been broken into and looted, worthless contents like clothes and personal effects strewn over the carriage. A wide-eyed vagrant rests in an upturned crate, nursing a pitiful campfire and muttering to themselves.
• Passenger car: This portion of the train is dedicated to those who actually want to be on the train. Those who have paid for a place on the train that is quiet (relatively) and pleasant (again, relatively) and guarded. The passenger cars are like whole towns stacked three houses high, with gangways and catwalks crisscrossing above and up into the shadowed vaults  of the carriage's ceiling. The carriage is free for passage through, but each apartment is sealed tight from the inside, and good luck convincing anyone to open their door. People can spend their entire lives on the train. Indeed, entire generations live in the carriage-apartments. Waiting for their destination or trading for their room as one of the engineering crew, them and their children forever bound in servitude in exchange for a safe place to rest.
• Dining car: Less of a restaurant, more of an abattoir. A hectic marketplace, a teeming mass of feeding and bizarre livestock which thrives in the dim light. The stench would be unbearable- rotting meat and vegetable matter to be carted off to the furnace at the front of the train. The bodily odor of a hundred different animal species all mingled together. There are creatures here whose tastes are somewhat singular. One might have to watch out that they don't get mistaken for the next piece of cattle to come up for auction...
• Plants have overgrown this carriage: A piece of cargo containing a particularly aggressive vine got broken, or holes in the carriage to the outside started letting in water and plant matter. The carriage is seething with greenery and insect life. There might be a cool breeze, even edible fruit or vegetable matter. Like a self contained biome, the carriage breathes, respiring within itself. Or perhaps it is not plant matter, but alien fungal growth that has overtaken the carriage. The air would be thick and heavy, full of spores. Luminous, fleshy fungi would line all the walls and floors. Poison everywhere.
• A prison carriage: The train as a prison sentence would mean life. Life imprisonment in an iron tomb. A screeching, roaring, hammering tomb that moves forever further from your home, from your life. Spending their days in barred cages amidst a mass of groaning metal, fed nothing but scraps from passing charnel carts, brutalised by guards who share a similar fate- to be forever aboard this train. The people and not-people imprisoned here would be driven mad soon after their arrival. Screaming, wailing, crying, cursing, they live a transitory mental life, their minds soon succumbing to the stress, the cruelty. The smell of bodily secretion, excrement, sweat, and blood permeate the carriage as the players move along corridors lined by rusted bars and concrete. Light in the carriage is largely regarded as a waste of oil, and prisoners lurk at the back of their cells as light approaches, their eyes not used to the flaring, searing pain of a lantern or a torch. Some of the cells are empty, others have clearly been broken out of... The escaped criminals would probably not stay in the car. They would run tearing away from the place as fast as their legs could carry them, but no guards would even bother to give chase. As far as the guards are concerned, they're not getting off any time soon. They would probably run off to seek solitude, to seek a way off the train, or to find a quiet place to die, to drown, to lie forever.
• Corpse car: 'Coach D is the designated quiet coach.' Where people can go if they wish to remain undisturbed. A sepulchre of stone built to blot out the engine noise, carpeted with a layer of bone dust. It also means that the creatures here would be rather distressed at the intrusion of noise. Adventuring parties included. This coach would be stacked full of coffins of every conceivable shape, size, and material. Wooden caskets piled indiscriminately on top of finely carved stone sarcophagi. Insectoid cocoons made from spittle and mud attached to the walls and suspended from the ceiling by transparent strands. Giant's tombs and exposed ossuaries waiting for the train to stop at some far-flung cemetery, where loved ones can be put to rest in the places of their distant ancestors.
• This carriage is full of machinery: The noise here is louder and more incessant than other carriages in the train. Unbearable crashing and hammering of pistons, roaring steam assails your senses as you stumble through this carriage.
• A shanty town: A community of vagrants has cropped up in one of the carriages. They have banded together for security and companionship, cobbling together their resources. The town is not a sanctioned passenger car, and the law keepers on the train frequently raid the community. But for now it is relatively peaceful. If one finds a place to rest here, they might hear music echoing off the walls high above. They might even find that the rocking of the train is somewhat soothing. They might.
• A feral carriage: The door is marked with an 'X' painted on in red. The contents of this carriage have been written off as lost. There are people or creatures in the carriage now that are openly hostile to any interlopers. Feral humans who cannibalize their own, chitinous monsters that lurk in the heights of the carriage, waiting to descend and prey on a likely morsel. The carriage smells of blood and death, and chattering can be heard from the deep recesses where light cannot fall.
• The water tank: Like a miniature oil-slicked ocean, this carriage provides the water the train needs to power the pistons which drive it ever forwards. It also provides passage for the train's aquatic passengers. Adventurers gaze upwards through steel-ribbed glass tunnels, seeing skeins of light pouring through rainbowed patterns of oil and indistinct forms drifting through the swill. Ancient species that have been on the train for aeons can be seen lurking on the bottom of the tank, staring with bulbous and glowing eyes from amongst ersatz reefs of rusted iron and banks of silt. It might be a sign the party is nearing the front of the train- the driver's cabin and the locomotive engine itself. Perhaps a mighty Aboleth lurks in the waters, looking to enslave passers by to strive for its freedom.
• The locomotive engine: The party has reached the front of the train. The engine that pulls the train ever further from whatever abyss it originally emerged. The noise here would be deafening- rank upon rank of immense pistons chug and scream and hiss while the furnace is fed by a never-ending stream of coal, oil, waste, bodies, anything flammable. No one the players have encountered had any stories about the driver. Even the engineering crew have never met the driver. There are rumours that the driver is a demon, a fallen angel, some abomination from the far places of the multiverse. Some say the driver is just a person, aimlessly hauling on myriad levers that number in the thousands, scrabbling at dials, and checking the pressure gauges. In any case, the driver would be dependent on the cosmology of any system currently in place. Could be anything. Could be nothing. Maybe there IS no driver. Maybe the driver is the latest poor soul to reach the cabin and find no one at the controls. They desperately try to bring the train to a stop, and spend the rest of their life figuring out how whilst being driven mad by the noise. Oooohhhh...

I imagine it looking like something akin to Battlefleet Gothic, but without the space guns.
Concept art by Zachary Graves

Encounters/events

So that the slog through doesn't become interminably dull, events crop up. During the passage through the belly of the train, various encounters the party might have with its denizens could include...

• A conductor: An unfortunate ticket inspector who became separated from the rest of the crew. 'Tickets please' doesn't even enter into their head as they're stumbling lost through the myriad carriages. Though perhaps they do ask the players for tickets... They probably wouldn't be able to read the cryptic scrawlings that pass for a valid ticket, inscribed on vellum and issued by some deep and unfathomable pseudo-divinity hundreds of years in the past. The worst the conductor could do in the event of an invalid ticket would be to respectfully ask the stowaways to alight at the next stop. When and where this might be, the conductor could not possibly know, however. (Aside: These tickets valid for travel aboard the train might be handed down from generation to generation on the material plane- each inheritor waiting for a chance to find the train, to use the ticket. They obviously don't know what it's really like on there. No timetable, no destination. Horrible.)
• A door to the outside: A solid iron valve-wheel door as high and wide as five people, or little more than a hatch. A sign next to the door says 'Door will not open while train is in motion.' There is a 50% chance that creatures congregate around the door, desperate to leave the train when it next stops. There could be a meager camp of disheveled and hungry vagrants clustered around it, running out of food and supplies with a jealous glint in their eyes. Or a long-dead party of adventurers. People say the longer you wait at the door, the closer to home you will be. These people could be mad.
• The engines become quiet: The train's engines thrum and pound, but grow slower and slower, the incessant pitch descending as the engines cease to strain, but the crashing sounds of the wheels on the tracks remain. Is the train going downhill? Perhaps the land beneath it has stopped. Perhaps gravity has ceased to be a burden.
• The wheels cease their thrumming, crashing noise: Almost as if the train is no longer moving on the tracks. The noises of the engine whir around you, but the noise sounds muffled. You become aware of a ringing in your ears. Now the noise is lessened, it is apparent that the train is slowly deafening you.
• A window: The window could be caked in soot, inside and out. Or slathered in paint or grease. Either way, it is difficult to see through. Someone looking through might make out indistinct shapes. Trees, mountains, the walls of a cave. Lights of uncertain origin flashing by at regular intervals. A glowing landscape of red-hot mountains. Shadowy masses of leviathans in the deep waters. A sweeping starscape.
• More people lost aboard the train: They might be able to tell the players what lies in the next carriage. They might have stories of their own. Injuries- a crippled foot, a heavily bleeding bite.
• An announcement: Some creature aboard the train- a conductor or a wayward passenger- has reached the broadcast terminal near the front of the train. Could be an official train message like 'we will shortly be arriving at KRRUUAADGIYDGHDSGHHHGHHHHH', or 'the dining car is now open. We are serving an array of cuisine from the deep oceans of ISEEEEEGHISDUUHBGAI, baked uterine tissue from fresh GNMASGOAOSSFOOOOGLLEL cattle, boiled cephalopod offal, fresh bacon rolls, sandwiches, and a drink of your choice.' Or perhaps a desperate voice imploring the passengers to rise up and seize the train, for the good of all those trapped on board, and then a sickening noise followed by silence.
• The food trolley: A slimy, seedy merchant pushing a comically large and unwieldy trolley packed with goods from the dining car comes trundling along. They are probably wearing an oversized coat stuffed full of extra-special products. Bottles of spirits (liquid and ectoplasmic alike), intricate contraptions and exquisite jewelry. Possibly legit, possibly not. It's hard to tell. But there would definitely be many a squeaking wheel. The merchant seems of uncertain origin, and it's likely they have spent their entire life on the train. Besides the sundries and salvaged goods they sell, there might be a great deal of information available to an astute questioner.
• The train begins to turn: With a convulsing of the engines, the train sways ominously. Your footing becomes unsteady and you must struggle to stay upright. Hold on to something, but be careful what you grab. Burning hot pipes are everywhere.
• The engines roar louder: The train might be encountering a patch of difficult land. Or ocean. Or non-land. A more viscous transitional medium. The noise of the machinery and steam builds to an unbearable cacophony. Speech is impossible to hear, and perception checks for sound are nigh impossible.
• The machinery begins to scream: With the mechanisms screeching and trembling, it becomes apparent that the brakes are being applied. The train is slowing down. Is it coming to a complete halt? All aboard can only wait, and hope. There is a mad rush for the nearest door as the trains inhabitants jostle and scrap amongst each other.
• Inter-planar travelers: For some, the train represents a way to transition through the walls that separate the planes, a way to traverse the soundless depths of the multiverse. They cannot control its direction, but sooner or later, it might pass through somewhere interesting. These travelers embarked to see the universe. A rash and venturesome decision, but one driven by a wild wanderlust. Getting off the train, however, is another matter... They each have stories of their own home, their origin. Some of them wish to return. Others realize they never will.
• A fugitive: A desperate miscreant evading law-keepers. The train would be a perfect place to hide. Its constant wending and shifting through dimensional boundaries makes it supremely difficult to follow, and those that make it aboard to look for the escapee would find it even harder to return, providing they even caught up with their quarry. Conversely, the party might find...
• Law-keepers looking for a fugitive: Perhaps there are indeed those aboard who are looking to apprehend someone who has evaded justice. But their task quickly changed. Instead of finding whoever it was they came for, their main concern would turn to simply staying alive long enough to make it off the train. The seekers would realize that this place is punishment enough. An eternal, mobile purgatory.
• Repair crew: The train requires constant maintenance, and those who are tasked with its repair would spend weeks, if not months or years attempting to find and fix any malfunctions. The train could be like a broom which had its head and shaft replaced intermittently for a million years but a billion different people. Same broom? It really doesn't matter. They can't get off anyway. The engineers of the train are covered in grime, dirt, oil. Wearing overalls and goggles, they scour the train in gangs, carting around scraps with which to patch holes in the pipes and the walls. They build and build and paint and hammer and build, working their way ever onwards down the train. Do they ever come back? Who knows?
• Inter-caste conflict: Two groups of engineers are encountered, going at each other all hammer-and-tongs. There is bad blood here. When the dust settles, it is apparent that there are subtle differences in the way they dress and the tools they carry. Perhaps there is a bitter conflict amongst different castes of the engineers about how best to care for the train. One caste's elders eschew a certain welding method which is deeply sacred to another, and one disdains the use of certain tools held to be holy objects by another. Either way, the conflict would be brutal. Not that anyone else would care, as long as the train keeps moving.

The combine from Half Life 2. Like this, but more ... messy.

How does one leave the train? How indeed. There must be a myriad of ways to get off, but they would be secret. Hidden. Difficult. There might be interdimensional doors that lead to innocuous places in various planes of existence. The door in the back of  an inner-city bakery might lead directly to one of the freight containers on the train. A sewer grate might give access to the dining car, and likewise provide a method of escape. The train might actually stop, allowing hundreds of desperate passengers to alight in what could be a lush paradise, or blasted wasteland. Either way, whole cities of displaced people could spring up. Perhaps the party separate the locomotive from the rest of the train- decoupling and forsaking the entirety of the rest of it to ... gods know what. Entropy and death? A welcome silence? The biting cold of outer space? Well, whichever, they then use the locomotive's interdimensional powers to go have some really weird adventures. If they can ever figure out the controls.

Eh. That's enough about trains. I don't even like them that much...