I've got D&D settings up the proverbial wazoo. If I ever wanted to play D&D (which I often do), the most difficult part for me would be to decide which setting to use. I've got Greyhawk, which has years of nostalgia behind it. Speaking of nostalgia, I've got the broad overview of Mystara that came with the Moldvay blue-box Expert Set and Module X1: The Isle of Dread, and as I was looking over it last night it occurred to me that it would make a fun setting to just up and run with; I've got Birthright, my favorite setting; Eberron, which I got from someone else but have never really thought much about (aside from the Warforged, which are cool, and the pulp/noir-influenced illustrations); I've got every edition of Forgotten Realms, a setting I don't love but can't ever seem to let go of entirely; Dark Sun, which I've been planning to adapt as a replacement for Marac in Earthdawn; Spelljammer: Shadow of the Spider Moon, a lovely rewrite of Spelljammer for Polyhedron Magazine, complete with Alphonse Mucha-influenced artwork; I've got the alternate world of Yrth from GURPS Fantasy / Banestorm, which I've been slowly converting to d20; and tons of historical settings by way of books like Charlemagne's Paladins and A Mighty Fortress to Avalanche Press's Vlad the Impaler and Last Days of Constantinople to Green Ronin's Medieval Player's Handbook. I've probably got a few more settings besides these that I can't think of at the moment, but suffice to say, I don't really have a need for a new setting.
A while ago, Jeff Rients mentioned on his Gameblog that he had long considered undertaking a challenge to create a D&D world using the old 1st Edition Fiend Folio as its primary monster manual. Someone in the comments section of his blog said that once they finished up with their steampunk campaign, they'd like to try making a Fiend Folio-centric world. I initially mis-read that entry and thought he was proposing a steampunk world based around Fiend Folio, and my mind clicked.
Since then, I've been throwing together a basic setting, which culls liberally from various sources, and I call "Black Smoke and Red Sands". It's based around the fusion of Planetary Romance and Victorian Steampunk. The basic conceit of the setting is that in 1876 or so, magical portals opened up in London and a few other places on Earth. These portals led to Mars, which was pretty much along the lines of what Percival Lowell imagined: great red deserts criss-crossed by canyon-like canals, sustaining a dying world. In fact, the Martian civilization had left numerous ruins in the canals - and even more grandiose and ancient ruins on the nearly-airless highlands - but none of the Martians themselves remained...unless one could consider the numerous mischievous and malicious creatures collectively known as Gremlins to be the Martians, but such works seemed impossible to have been constructed by such small-minded creatures.
In exploring the Martian canals, the British (and many others after them, including the Germans, French, Americans, and Greeks) discovered two amazing things. The first was Martian sorcery - magic was the art upon which the Martian civilization was built, and it was to the amazement and fascination of xeno-archaeologists that the mysterious formulae and incantations actually produced consistent "miraculous" effects. Under scholars like Camille Flammarion (a real-life influence on Percival Lowell), the "Martian Science" is beginning to be cataloged and codified.
The second discovery was that of more portals, leading to other worlds. Portals have been found which lead to Venus, Mercury, and other places, all of which are at least vaguely habitable. Mercury has provided a wealth of mines to exploit for those who dare to work there (it's become the new dumping-ground for criminals), and Venus, with its steaming jungles, is a great source of lumber and exotic drugs and medicines. Another major resource which has been exploited are the Dakon, sentient ape-like creatures who walk upright and speak. The Dakon have largely been enslaved by the Imperial powers, removing most of the demand for African slaves on Earth, but introducing new theological quandaries for the Church.
Now it's the 1890s, and colonization of Mars (with plantations on Venus and mines on Mercury) is well-underway. The technological advances made possible by Charles Babbage, Nikola Tesla and the rejuvenated Greek Empire have given the Imperial powers everything from steam tanks to clockwork limbs to lightning guns with which to subjugate the savage Red Planet. The discoveries of Martian sorcery and technology have caused wizardly societies to rise to prominence (as well as cults devoted to hoary alien Martian deities). Some wizards - working with the Gremlins named 'Svirfneblin' by the Norwegian who discovered them - have combined the sciences to create self-aware automata and other strange wonders.
Yet no one suspects the true reason for the Martians' disappearance...and why the Dakon fear and hate their memory so deeply.
This setting is built upon many influences. I've grabbed ideas from Space: 1889 and GURPS Steampunk's "Etheria" setting, with "Stargate SG-1" and a touch of Castle Falkenstein's sorcerous orders. I also threw in some other stuff I hadn't yet used but wanted to, like Phil Reed's Construct Mechanus. As I went through the Fiend Folio, I found that most of the races and monsters divided nicely between Martian "gremlins" and magical constructs, and Venusian hot-climate dwelling beasts. And while I wanted all the standbys of Victorian adventure and hissing, clanking steampunk, I also wanted things on the frontiers to be really rough-and-tumble, justifying a more Sword-and-Planet attitude of Burroughs-style swashbuckling and savage action (as is fitting for D&D). Colonial Martian culture is becoming something quite different than stolid, refined London civilization - Mars is infecting humanity.
Since this blog is really about cataloging ideas and not writing teasers, I'll spill the whole of what I've been thinking:
The Githyanki and Githzerai of the Fiend Folio are the remnant peoples of the Martian civilization. The Martians' devotion to magic resembled something like that of Moorcock's Melnibone, and affected them similarly. They became decadent and corrupt, thinking little of the damage they did as they wielded power to bend nature to their will. They created the portals, discovering lands beyond their own world to conquer. Unfortunately, one of these portals led to what we know as Pluto - a frozen, hellish ball of rock containing chamber upon chamber of hibernating Illithid - those the Martians came to know as the "Mind-Flayers." They had no defense against their psionic assaults, and were soon subjugated. Only millennia later was Gith able to raise a rebellion against their masters. However, those who followed after Gith chose seperate paths to liberation: the Githyanki relied heavily upon necromancy to bolster their power, while the Githzerai forged an unholy alliance with a Venusian power, the savage and potent Slaadi. The Githyanki would not allow themselves to be made a subject people ever again, and so the two factions split to become mortal enemies. Their war of liberation was never really completed; even now, they dwell in strange lands beyond the portals, plotting their next move.
And, of course, the Mind-Flayers are still out there somewhere.