I'd originally thought of this setting as being some kind of vague real-world-but-exaggerated bit. Some kind of William S. Burroughs supernatural elements / magical realism was part of the plan, but I didn't really know where I intended to go with it. Now I'm reading Naked Lunch, though, so I've got some new ideas.
First of all, Interzone--the otherworldly omni-city of Naked Lunch--is a blatantly, obviously awesome setting for a roleplaying game. Get a load of how Burroughs describes it.
The room seems to shake and vibrate with motion. The blood and substance of many races, Negro, Polynesian, Mountain Mongol, Desert Nomad, Polyglot Near East, Indian -- races as yet unconceived and unborn, combinations not yet realized pass through your body.
The Composite City where all human potentials are spread out in a vast silent market.
Minarets, palms, mountains, jungle... A sluggish river jumping with vicious fish, vast weed-grown parks where boys lie in the grass, play cryptic games, Not a locked door in the City. Anyone comes into your room at any time.
All houses in the City are joined. Houses of sod -- high mountain Mongols blink in smokey doorways -- houses of bamboo and teak, houses of adobe, stone and red brick, South Pacific and Maori houses, houses in trees and river boats, wood houses one hundred feet long sheltering entire tribes, houses of boxes and corrugated iron where old men sit in rotten rags cooking down canned heat, great rusty iron racks rising two hundred feet in the air from swamps and rubbish with perilous partitions built on multi-levelled platforms, and hammocks swinging over the void.
Expeditions leave for unknown places with unknown purposes. Strangers arrive on rafts of old packing crates tied together with rotten rope, they stagger in out of the jungle their eyes swollen shut from insect bites, they come down the mountain trails on cracked bleeding feet through the dusty windy outskirts of the city, where people defecate in rows along adobe walls and vultures fight over fish heads.
In the City Market is the Meet Cafe. Followers of obsolete, unthinkable trades doodling in Etruscan, addicts of drugs not yet synthesized, pushers of souped-up Harmaline, junk reduced to pure habit offering precarious vegetable serenity, liquids to induce Latah, Tithonian longevity serums, black marketeers of World War III, excisors of telepathic sensitivity, osteopaths of the spirit, investigators of infractions denounced by bland paranoid chess players, servers of fragmentary warrants taken down in hebephrenic shorthand charging unspeakable mutilations of the spirit, bureaucrats of spectral departments, officials of unconstituted police states, a Lesbian dwarf who has perfected operation Bangutot, the lung erection that strangles a sleeping enemy, sellers of orgone tanks and relaxing machines, brokers of exquisite dreams and memories tested on the sensitized cells of junk sickness and bartered for raw materials of the will, doctors skilled in the treatment of diseases dormant in the black dust of ruined cities, gathering virulence in the white blood of eyeless worms feeling slowly to the surface and the human host, maladies of the ocean floor and the stratosphere, maladies of the laboratory and atomic war.... A place where the unknown past and the emergent future meet in a vibrating soundless hum... Larval entities waiting for a Live One...
I could definitely work with this. Or something like this. The idea of a city outside the normal world--one which is the apotheosis of all cities, where all things and all peoples can be found--sounds extremely fun and game-friendly.
First of all, it's about time I actually defined Edge City itself. It wouldn't be my Interzone ripoff, but instead a relatively normal city on Earth. Specifically, it'd be something like a little New York located on the American West Coast, a jumped-up suburb near L.A., reborn in the 1950s after a vast crack opened up in the earth, swallowing up a quarter of the town and cutting the rest off from easy access. The remains of the settlement--popularly renamed "Edge City"--went a little weird after that, developing an odd, insular culture of its own through its partial isolation . . . and constant exposure to the influence of that great rift in the Earth.
The earthquake, of course, wasn't wholly geological in nature. It was largely the result of an intermittent dimensional weak spot which opened up at a fault line at exactly the wrong time, dumping thousands of tons of bedrock and several square miles of American city into a ragged, spacially-convoluted continuum between worlds. Haven't got a good name for it, really, so I'm just calling it "the Between" at the moment. I'm picturing it as an endless, cluttered gulf of psychedelic sky, with a breathable atmosphere and something of a do-it-yourself gravity situation.
The indigenous life of the Between tends to look like abyssal and prehistoric sea life, often with strong tendencies towards infectious, parasitic, mutational, and addictive qualities (all very Burroughs, of course). In some places, it mirrors Earth life forms in ways that suggest the Between doesn't follow the familiar processes of evolution or inheritance.
Different regions of the Between are "closer" to different worlds, so stuff that falls through from Earth tends to end up in the same general area. And this is where the Interzone shtick comes in. People from (and pieces of) Earth have been finding their way to the Between one way or another throughout all of history, and they've come together as a sort of composite city, a drifting cluster of broken landmass, linked by ropes and chains and iron rods, all encrusted by architecture in every conceivable style, some it it reclaimed from terrestrial wreckage, and some of newly built in the Between out of alien materials. I'm not sure what to call this city--Croatoan? Limbo? Gateway? The Tatters?--but I do know that getting a chunk of (what later became) Edge City added to its bulk half a century ago had a significant impact on its culture. Along with that slice of 1950s urban/sub-urban landscape, it also got a number of armed and experienced 1950s gangsters. They became a powerful new political faction in the Between, and introduced a new kind of drive and organization to its inhabitants.
The old mob from the '50s has since fragmented and mutated, inevitably being changed by the Between as much as they changed the Tatters (or whatever). Now there are Maoris and Germans and weird, semi-translucent fish-things all wearing pinstripe suits and fedoras, wielding tommyguns and smuggling goods from a hundred different worlds. Some of the old guys are still alive, sustained by alien drugs, but they're looking less human than the fish-things, these days.
And they don't just confine their operations to the Between. It's actually easier to get back to Earth than it is to get to other free-floating islands. So various types of shady individuals from the Tatters tend to come through to Edge City--via the Crack, of course--from time to time, creating in a cross-dimensional black market in alien drugs and weapons, and some very, very strange pornography.
...So the angle I want to work in Edge City itself comes from some of the elements of Jack Kirby's Intergang, along with some episodes of Angel, and Torchwood. Oh, and Unknown Armies, of course. Basically, the whole otherworldly underworld bit, where there's this large, weird, hidden subculture fighting amongst themselves for power and profit, all without the world at large ever knowing.
One complicating element might be the fact that matter from the Between isn't quite the same as matter from proper dimensions. In places like Earth's universe, it just doesn't last. So humans who've lived in the Between for a while, subsisting on food made out of local matter, tend to have trouble if they return to Earth for too long. Those born in the Between have it even rougher. And native life forms, of course, have the most trouble outside of the Between, having a tendency to simply dissolve within hours or days if they can't consume and metabolize a great deal of local matter very quickly.
Just how one gets to the Between and back is something I'd have to figure out, of course. The Crack at Edge City started off as a minor contact point which became much more significant when the earthquake dumped a huge amount of mass through it. I like the idea of heavy or prolonged usage making gateways more reliable, and also frequent passage making crossing over easier for a given individual. Maybe if you've been across often enough, you don't even need to find an existing gateway, but instead can just push through by yourself. Also, maybe consuming food (or, of course, drugs) from the Between makes it possible to find or make gateways, or to see otherwise-invisible alien artifacts. There's a bit in Naked Lunch about "Black Meat, flesh of the giant aquatic black centipede", traffickers in which "exhibit paralyzed crustaceans in camouflage pockets of the Plaza visible only to the Meat Eaters". For Burroughs, it's obviously a big junky subculture metaphor, but I really love it as a sci-fi concept.
Okay, this post is already too long, and I haven't even gotten around to discussing the other idea I've been toying with. I'll try and post about that soon.