I'm not putting this in 'It's My Own Creation' because it's not choate enough to be a campaign setting. Right now this whole project is just IDEAS. I'm pitching it to you guys, getting opinions and input, trying to see if there's any merit in the whole thing.
The world used to be a pretty swell place until magic came. Then it changed the world for the worst.
Even though FTL-travel hasn't been invented, Orion Drives did allow people to travel places within the solar system and even discover intelligence in their neighborhood. All of the contact was peaceful by the way. On the Earth-analog it's basically a utopia. Crime is really low; racism, sexism, religious strife, and dictatorships are a thing of the past; replicators and free energy exist to an extent that the Gini index is in the mid .90s, genetic engineering has wiped out disease and has made the human lifespan 250 years; so on and so forth. Artificial intelligence is just in its infancy and the smallest AI is the size of a two-story building, with it getting smaller all of the time. Neuroscience has advanced to the point where mind-uploading and intelligence enhancing is tantalizingly close, which would make humans and androids indistinguishable.
In a parallel universe, meanwhile, magic and gods reign supreme. The world is a blighted, barely-existing landscape like it is in Dungeons and Dragons. In other words, life is like a combination of the worst parts of the Dark Ages, the Inquisition, and the subjugation of African and Indian nations made worse by random dragon attacks and kept on top by a magical aristocracy. Unfortunately, like with have most people have said most D&D-verses should have happen to them, there was one too many apocalypses and the magical world was dying. The Gods hatched a scheme to use a ritual to fuse their worlds with the closest analog so that they could continue to exist and run the world the way that they wanted to. They called their world the Light World and the modern world the Dark World. They were also aware that the Dark World would never accept their way of life let alone worship them, so the only resort was to destroy those governments in a pre-emptive strike and install themselves as leaders.
Which totally happened. A flood of magical phenomena hit a totally unprepared world, causing governments to collapse and destroying interplantary travel--causing races not native to the world to be stranded where they are. With the population temporarily subdued, they initiated the World Fusion ritual which transplanted landscape and cities and entire populations right onto to Dark World. The people realized what was happening and fought back and though the World Fusion ritual stripped a lot of the magical powers of the immigrants and the gods the Light Worlders still managed to win. They installed themselves as rulers again and went back to their old ways of dragonriders battling over cities for land and elven aristocrats living in opulance while the city starved.
Magic isn't automatically bad in the sense of the Dark Side of the Force; it's possible to have constructive uses for it. The problem is that the destructive uses for it outweigh the constructive ones. A team of wizards can totally level a metropolis if they're not stopped and a lot of wizards are selfish enough to do so. Of course to prevent things from devolving completely into D&D with a blasted Points of Light landscape, the really destructive magic is rare. They're like nukes in Shadowrun; they've happened many times but society doesn't collapse from a few or even twenty of them. The problem is that much of the more powerful magic (dragon magic, elven magic, etc.) is genetically determined, such that most of the magical tools couldn't escape into the hands of the masses. Even if the Magocracy had a change of heart it wouldn't make the world better because magic is limited in constructive potential--they'd still need to go back to the old science.
Science has suffered a huge but not permanent setback.
In the bad old days, it was totally possible for 100 knights to take on a village of 5000 peasants and win. In addition to the massive gulf in equipment, there was also the issue of training and nutrition. Today, not so much; at least in places with technological similarity between the military and the populace. The people who hold the magical tools are aware of this and world like to completely stamp out science... the problem with it is that it gives too much of an advantage to the competing magical factions to fully abandon; the Darklands simply cannot collapse without modern agricultural techniques. Kefin, the City of Sand, would collapse entirely without plumbing and power systems to run the plumbing. So while technology is very assymetrical, even in the same location, it's not as if you couldn't find a working computer or RV if you looked hard enough. The magical forces would also love to eradicate inconvenient social sciences and humanities and take great pains to do so, but there is so much geegaw left out in the lands that you can seriously stumble upon a CD that contains the entire scanned contents of the New York Library on it.
The people have memories of their utopia.
It's only been about 40 years since the collapse of the old world. And people are pissed that they had to give it up. People live with the knowledge that they're going to outlive their grandchildren with genetic engineering surpressed (and told that this is a good thing, since exceeding your natural lifespan is wrong), things we take for granted like chocolate and oranges are reserved for the upper classes, people are facing arbitrary amounts of discrimination, and that they're going to have to TILL the SOIL. In some places the social engineering has advanced enough that people aren't automatically against the new government but for the most part the people who didn't come from the fantasy world or are on the top of the social ladder hate it. Unlike in most fantasy, people can imagine a better life than mud farms and terror.
Not to mention the fact that even though the old society has collapsed doesn't mean that it's completely gone. While it's true that most of the Dark World cities resemble those of Fist of the North Star or Mad Max, it's not like you can't go downtown and at least not see where the City Hall and the amusement park used to be. Some of it even still works, especially by the lucky few who has enough magical power to get things to run for a few seconds.
Long-range travel is difficult but not impossible.
Even though the old world has collapsed and there aren't things like maintained roads and gas stations, it's not like it's necessarily impossible to make a cross-country trip across the United States in four days. There are still some vehicles if you can get them and if you can avoid the roadsign gangs and the random monsters and somehow manage to scrape up enough fuel you could conceivably do it. So someone in Brazil claiming that they just moved from Canada is really unusual, but not impossible. The same goes for communication. The Internet, propped up by secret societies and sympathetic mages exists very sporadically but it exists. If you really want to and you're willing to risk it you can totally tell your cousin in Mexico City that the weather in Bombay sucks ass due to the aftereffects of a spellplague storm.
The Gods are real and they're petty.
Gods like Zeus and Lovitar and Thor totally exist and they totally grant superpowers. In fact they're the whole reason why the fantasy world was able to cross over with the modern world. Now while the Gods (except for Yahweh, but he doesn't exist in this setting ) aren't baby-eating evil they behave exactly like you would expect personifications of domains and elemental embodiments in a privileged class with a vested interested in the status quo to behave. That is, stories like Arachne and Job totally exist and happen and Poseidon will totally sent a tsunami at your city if you piss him off enough. Some of the nominally 'good' gods like Anansi and Bahamut are aware that they're totally making the world worse and angst about ruining the lives of people who were better off without them, but for the most part they act like the gods in classical mythology. However, while very powerful they're not invincible. A person, even a Dark World native, could accumulate enough power to totally blow Ganesh's brains out. It's just very hard; the Gods function more like the Legion of Doom in this way, only they already own the world.
The people can theoretically make a stand against this brave new world.
Since the Dark World used to be peaceful, there was no need for standing militaries or complicated weaponry; needless to say they got blindsided by the Light Worlders. But the invasions and World Fusion ritual has unfortunately stripped a lot of their magical power. While organizing a force to take on the Necromancer's Guild that has taken root in Detroit would result in huge casualties (not least because the halflings are barely on their side), it's not an automatic loss for the non-badasses like in D&D. You simply cannot gain the amount of power in this campaign setting necessary to make big changes in the world on your lonesome. In fact at the time period at which the campaign setting is set a few major cities have managed to kick out their fantasy overlords. There is going to be a reprisal of course, but it shows that rebellion is totally possible.
While the muggles so to speak are kind of restricted on what they can do with magic, there is still other supernatural phlebtonium to help them out. Psionics is available as an alternative for people who don't have magical talent. Non-arcane super-science totally exists. Even divine magic works and you don't necessarily have to schtup a god in order to get access to it; a guy can totally pray hardcore to the nature deities for several years and become a paladin. And if you don't have a nameable form of phlebtonium, people have totally seen a so-called mundane warrior slice an iron golem in half with one swing of a butterfly knife. Arcane and divine magic are only on top because it's easy to control their access to the population at large and you can gain huge superpowers from them without really working very hard.
Extra-terrestrial races; what's up with that?
Oh, they're there. You have races like your Vulcan-analogue, your Turian-analogue, your Asari-analogue, etc.. Because you're fusing them with the typical stable of fantasy races it may not seem necessary, but it seemed to imply unfortunate things about races (even if they're just fictional) if we made it so that only human beings got oppressed by those mean fantasy races. So if nothing else you have to have intelligent species other than humans in the setting.
Travel to other worlds is still quite possible. If not with the handful of spaceships still working then with magic. This is not available for most people unfortunately so chances are if you see a non-Earthling on Earth they've been stuck there ever since World Fusion. The background of 'I came from another planet' isn't impossible but it's definitely not something you can casually claim like 'son of pirates' or 'was a war profiteer'.
So what does a typical adventure look like?
Imagine a combination of Mad Max and Shadowrun, leaning in the former direction. In Shadowrun, society is pretty much impossible to defeat. In this game, it's possible but VERY VERY hard. You and some other sociopaths can totally accumulate enough power to beat up the entirety of Seoul's police force if you're that much of a bastard. Because communication is so spotty, even with the remnants of the Internet, you can level a few villages out in the boonies then head cross-country and probably not have to worry about paying for it. Just like in D&D. This means that you don't have to take the extreme precautions and anonymity worship that you do in Shadowrun, but the vast majority most sociopaths still have to obey the law. Cities do collapse now and then because of assymetrical power accumulation between individuals and society and it's just a fact of life.
Now even though this is the ruins of modern society, people can still find guns and artillery and stuff. Obviously the religious orders and magocracies fear them, even if they want them for themselves. It's just that such equipment is only really the gamechanger that it was in the medieval times because they weren't competing against actual superpowers. So even if they weren't rare, five guys with uzis wouldn't be an automatic win against a mid-levelled wizard. Twenty guys with uzis would still be a threat and hence why the powers that be are very serious about gun control. The point is that like in D&D, most combat takes place at melee range and especially at higher levels being a guy who wields a sword and classic armor is totally feasible. Again, think Mad Max.
So with that in mind, here are some sample adventures:
- Manticores have decided to take up nest by one of the old trailer parks by the lake. The people there would like to flee with their dilapidated vehicles, but the highway is blocked by a gang of gnoll slavers, putting the refugees between a rock and a hard place.
- A zombie apocalypse has hit one of the desert cities. While nothing can really be done for the place, there's also a hidden Internet relay station that connects Lisbon with the west border of Spain that went down. You must ensure that it gets repaired, remains hidden, and because the Powers That Be are aware of this you need to find some way to magically hide it, too.
- Going through classified files shows that there was an experimental FTL spaceship buried in the Arctic tundra. Unfortunately the area has shown that this area is guarded by neanderthals, snow elves, wendigo tribes, and other such nastiness. Since you won't be able to retrieve the engines and schematics yourselves you'll have to bring a team of explorers as well. You're supposed to keep them safe too so they can help you drag it back.
- The local water dragon spirit has been turning the swamplands' water brackish and diseased. You must either appease the dragon or pound some sense into his head.
- The Copenhagen Magocracy branch recently raided a hidden Internet cafe and imprisoned the computer techs along with the documents that they were trying to archive; the documents they were trying to preserve was the collection of the city's childrens' library. You must break into the jail and rescue them before they're publically executed.
- An airtight nuclear cruiser got Hex-Bombed Several years ago and crashed to the bottom of the Black Sea. Unfortunately, the Hex leaked into the reactor and has not only turned the crew into superpowered ghouls but is infecting the wildlife and sailors that pass through it. Your job is to make a deep-sea expedition and purify the reactor while also trying not to soak up too much radiation.
- There is a gang war in the east side of the dilapidated downtown of Philadelphia between the shifters and whatever you're calling the not!Turian. There have been reports of banned weaponry being used and if it gets out of hand it will attract the attention of the Magocracy.