Today I’m going to talk a little about something that I’ve thought about off and on over the years of playing D&D and similar games. In this specific case, that’s the cosmological structure of the elemental planes from the D20 system – the Inner Planes of the Great Wheel cosmology.
Specifically, in the Planescape cosmology, they took the familiar elemental planes – Earth, Air, Fire, and Water – and the two vaguely-mentioned Energy Planes of Positive and Negative that were the theoretical sources of the energy clerics channeled, and stirred up a whole batch of new demi-elemental and quasi-elemental planes. Ooze and Magma and Ice and Smoke, Mineral and Lightning and Radiance and Steam, Dust and Vacuum and Ash and Salt; planes with their own properties and characteristics that were new and interesting places in their own rights.
They stopped there, sensibly, because going any farther invites you to infinitely split the cosmological voids between each plane, asking “Well, what about this mix of elemental forces? What springs out of that? What happens in the conceptual space between, say, Ooze and Positive Energy?” Now and then I’ve poked around with this idea; at one point I even had a stack of about forty or fifty hand-written pages of the gradients between the elemental planes, although it’s long since been devoured by the passage of time and the entropy of these things.
The thing, though, is that you can play this kind of infinite splitting if you want – if you have a game system and setting that allows for something like this, you can infinitely split these hairs and fine ever-finer gradiations that can be made into entire planar worlds. The space between Ooze and Positive? That’s Wood, which could itself exist as a full element. The space between Mineral and Fire? You find Metal, also an element in its own right in some systems. Vacuum could already be Void, but if you split the space between it and Negative, you can justify an entropic Void that isn’t the raw entropy and undeath of the Negative, but which is a more perfect void than simple airlessness.
You can go on like this endlessly; split the space between Magma and Earth at the right amount and you may find a para-elemental plane of Coal, where you have everything from rock that will sluggishly burn with a fitful light to coal that exists as a nearly platonic ideal, burning brighter and hotter than anything from outside the plane.
So why am I talking about this? Because of the game possibilities it provides. If you’re playing a system with transplanar travel, consider the possibilities of being able to infinitely divide the spaces between the planes. (This works just as well for the conceptual planes of the model as well; split the space between any two given planes and you can possibly find an undiscovered on in the gap.) A system like The Strange, or D&D/Pathfinder, or the hypothetical Transplanar Express setting, or anything which allows for dimension hopping can make use of this.
Prospecting for new planes could be a dangerous but possibly lucrative business – and a rescue team for transplanar prospectors might be even more lucrative, as well as fraught with politics and intrigue. “We sent them out with the resonance frequency where there should be a plane, but we don’t know what happened – they haven’t checked back in. Can you send a crew to go check and see for us?” Did the prospector team find a plane and run afoul of native life? Or did they jump into an encampment of people who found the plane first and want it kept quiet? Or did they instead find a frequency that works for plane-jumping but one where no plane exists (or existed; maybe they jumped into the gap and their corporeal forms have served as the seed for a brand new plane to crystallize, resulting in the PC rescue team being the first discoverers of a whole new world.)
And then there’s this possibility – if you invert the Great Wheel cosmology, the Inner Planes become the outermost shell of existence. Build a campaign where no one knows about the idea of the Material Plane, much less the conceptual planes that were the Outer Planes. Give your players a reason to keep seeking in the gaps, between the elements, until they trip over the confluence of the elements and discover a stable and infinite expanse of mostly-balanced world. And from there, well, they can try to find a planar balance point where the elements are so finely tuned that they cancel each other out – the point where the conceptual planes exist.
Even without that, though, the possibility to dig deep and leave players wondering if they’ve found an entirely new plane of existence or just an obscure corner of a known one is something a GM can have plenty of fun with, particularly if the players don’t have access to teleportation powers that would let them resolve the question quickly. Are you in the Plane of Coal, or a corner of the Plane of Earth that exists around the concept that some forms of ‘stone’ can be organic in nature? Did you find elemental Shadow between the Positive and Negative planes, or just a shortcut to the Material-Plane echo that is known as Shadow? And what happens when the self-proclaimed Lord of the Plane of Ice decides that his para-element should be regarded as a true element and not a hybrid of Water and Air? Who can really tell him he’s wrong? The possibilities are vast, and this is all only the tip of what could be done with the idea of delving into the spaces between the planes that are known and familiar.
Give it a thought and see what you come up with!