I somehow got it into my head that the various types of worlds were theorized to be directly connected to their associated elemental plane--almost a projection of that plane into Wildspace.
Am I getting this from somewhere?
The only products I have are the original boxed set and the War Captain's Companion, and I'm pretty sure I got this idea before I had the latter.
The problem I'm having is that I've looked through the boxed set more than once looking for it, and I just can't find where it actually says that anywhere.
So...does anyone have a reference for the idea?
Maybe you are getting this from the idea that celestial bodies have four possible types:
- Earth bodies,
- Fire bodies,
- Air bodies and
- Water bodies
Earth, Fire, Air and Water bodies are not neccessarily directly connected to the Elemental Planes of the same name, but Jeff Grubb did suggest using monsters from the planes on them.
Earth bodies are essentially "normal" worlds, like Krynn, Oerth and Toril, so you can use them as a basis for how many portals exist to the Elemental Plane of Earth...and how many portals exist to other planes.
Fire bodies are essentially suns (or molten worlds) so it is a lot harder for creatures that are not from the Elemental Plane of Fire to live there, because most "normal" Material Plane races would catch fire on most fire bodies. Sirrion, in Krynnspace, is an example of a very very cool fire body that "normal" races can visit, but it isn't a place that PCs can live on permanently. You can see how portals from the Elemental Plane of Fire would be a lot more useful, if they connected to a Material Plane planet like Sirrion.
You could have earth regions on a fire world and you could have air on a fire world, but water would mostly turn to steam. So, I think you could have quasi-elemental stuff on a cool fire body like Sirrion, but I'm not too sure you would get a lot of water creatures without some sort of modification process (i.e. you might have some sort of "magma scavver").
Air bodies are Jeff Grubb's take on the gas giants in the solar system, although you could have smaller ones too. The critters that live on them (or should I say live in them) usually need to be able to fly, without landing. Although there have been some air bodies that have floating rocks or very tall mountain peaks. So "normal" races can go there, but they need to have somewhere to live that floats in the air somehow, and they need to be able to move around without falling to their death. Again, you can see how portals from the Elemental Plane of Air would be more useful, if they connected to a Material Plane planet that was an air body. There would be little to no land and hence little to no underground, so elemental creatures could arrive deep in the middle of an air body.
You could have a small solid core (as well as floating islands) on an air body, so it could have portals from the Elemental Plane of Earth, Elemental Plane of Water and the Elemetnal Plane of Fire. Elemental creature from those planes would not be much worse off than on an Earth body, although if they could not fly, they might not have so much freedom of movement.
Water bodies are either sea-worlds, where ships could land on the surface or something fairly similar. So aquatic races from "normal" worlds could go there. I have seen SJ worlds with solid ground deep below the sea.
You could have portals from the Elemental Plane of Earth below the sea, so long as there were elementals that didn't need to breath. But I would have thought that portals from the Elemental Plane of Fire and the Elemental Plane of Air would need to be above the surface.
I think some Spelljammer fans have proposed the sort of thing you spoke of, but I don't recall it. Maybe somebody over at the Spelljammer forum at The Piazza would remember a canon or fanon world that does the sort of thing you are talking about.