I've had another setting idea lately, probably using a variation of True 20 (as I wrote about
here). The basic setting up a world of islands on a vast sea, but instead of an archipelago the islands are mesas and mountain tops, with a sea of corrosive miasma covering most of the world. Water is as precious as gold, and trading airships cross the miasma, binding the remaining inhabitants of the world together. Below the miasma are the illithids, engaged in a long process of terraforming the world to be more to their liking, and the various creatures of the ecology that they're creating--stuff like
grick,
grell,
ropers, various
fungi,
aboleths,
otyughs, and other betentacled horrors. The point here to take the various monsters that D&D usually has as nightmare monsters from beyond reality and cast them all as parts of a single ecosystem.
Non-aberrations would also have been displaced by the miasma too, so there'd be conflict with ogres and kobolds and so on for the remaining living spaces as well as between nations over water and arable land.
The other idea I had, fueled by Planescape: Torment and
The War Against the Chtorr series, is that since the mind flayers are basically invading aliens terraforming the world in this scenario, have the
githyanki and the
githzerai show up as other aliens to battle it out with their ancient foe, turning the world into a three-way battleground. That's the high-end area of the campaign. The mid area is expeditions into the miasma to recover ancient artifacts and fight the ecosystem, and the low end is conflict on the mountaintops.
Fitting with the science fiction-ish theme, I'd get rid of standard wizardry and recast psychic powers through a sorcerous lens. Pyrokinesis would thus be "The Lore of the Flames," Empathy would be "The Lore of the Heart," Teleportation would be "The Lore of the Spheres," and Victorian-style spiritualism would be "The Lore of Whispers." Another part of the reason I want to use True 20 is that it's magic system is already basically psychic powers so there wouldn't be much converting required, other than reorganizating existing powers a bit.
Well, today I was reading my RPG RSS feeds and it turns out that
apparently Jeff Grubb came up with that idea twenty years ago.
It's mostly there, other than the githyanki/githzerai angle. Living on mountaintops, cloud sea, mind flayers down below, the works. He focuses on cloudsea versions of existing water monsters as a way to avoid the problems with underwater adventures rather than aberrations as a unified ecosystem rather than lolweird monsters, but the principle is the same. He also doesn't do anything new with the magic and doesn't have the science fiction lens, so I can legitimately feel like I take the basic idea in a new and interesting idea. Still, there really is nothing new under the sun.