Roman said:
In standard D&D cosmology and most other cosmologies created for D&D and d20 (in fact, all that I know about, but than again - my breath of knowledge on this topic is not particularly great) other worlds or other planes are basically material planes based on common physical concepts (there is still the concept of matter, there is the concept of space, characters and creatures there still have bodies, etc.), but with a theme attached to each of the worlds.
Has anobody tried something different - where in another world/plane of existence you do not have a body and things are just far more different than in the more 'standard' cosmologies? I would like to do something along these lines but am at the moment unsure where to start.
I think the key to success with planes is always to make them different but not too different

Different enough that the gaming experience (moving around, interacting with local people, using magic, dying...) is memorable for the players, but not too different to become a burden to run obviously.
I like a lot Gez's and Merak's suggestions, they are very good examples.
In our advantures I like playing with
space because that's pretty easy. Just along the lines of "non-euclidean geometries" (but nothing really difficult here), have weird things happen with
distance and
position on other planes, such as these examples:
Gehenna: the plane is made of 4 infinitely high volcanos; it doesn't matter on which one you're now, it's always in the middle of the other 3; despite the fact that the slope is not vertical, the distance between them is always the same; there is effectively no bottom below
Bytopia: the plane is made of 2 worlds facing each other; each world is a planet (walk enough and you'll be back here), but the distance between the 2 "floors" is about always the same, just like they were flat; there is day and night but no sun between the 2, just a radiance passing through the sky
Arborea: the world is made of infinitely-high trees and jungles, with no top or bottom, and cities are built where plants form a suitably flat area with leaves and canopy
Portal-towns: they exist in 2 planes at the same time, meaning that e.g. from plane 1 the city only has a South entrance, from plane 2 has only a North entrance, but from inside the town you see both exists (you exit on a different plane depending which one you choose); if you just "go around" the town, you're still on the same plane
For instance, IMC the Ethereal plane is always coexistant with the Material and has the same "space density", which means that (1) a point A in MP always correspond to a point A' in EP and (2) distance between two points AB in MP is always the same as distance between two equivalent A'B' in EP.
Otherwise, to make it different, the Plane of Shadows still has property (1), but not (2), and that explains why you can use the PoS to travel faster (or slower if you make a mistake). It also explains why a pebble in MP may corresponds to a mountain in PoS and viceversa.
Finally the Astral Plane doesn't even have property (1), at least not two ways: at every A in MP there's an A'' in AP, but AP has "lots of more points" not corresponding to any in the MP.
Then of course you can play with
time,
magic and
life. Just be sure you don't make common mistakes which lots of authors do, such as first making a world different and them trying to put back the normality. That's what they do for example when they fill outer planes with mortals living among the dead, or when they pretend to place different planes at a fixed distance, which basically turns planes into simply different locations... but if you take away the "extra-spacial" nature of planes, they're not planes anymore!
I to have the feeling that this design mistakes often "trivialize" the planes, that's why I have a nice time overriding them quite freely
