Warning: written while sober.
D&D’s interactions with planes are kind of funny. They’re the adventuring locations which you can’t just walk or even teleport to but instead have to go through the DM’s hoops, but also the land of the dead and the place where the angels come from.
But I just don’t like the Great Wheel, because it substitutes a (bad) psychology textbook for a world map. I just don’t like the Astral Plane, because it’s empty space. And so forth. Which is kind of crazy, because the D&D cosmology has a lot of pretty neat stuff in it
For instance: Is the ethereal plane a place (as it is in D&D) or a non-place? I kind of like the Ethereal as the wind between the worlds, the place you get when you take the place away. If it’s not a place, then of course it’s where the ghosts go, and of course it’s the empty place. Of course the thing that blocks off ethereal travel is stuff that makes a plane super thematic after itself: deep nature, ancient cities, political courts, monuments.
I don’t love the elemental planes as a neopolitan ice cream box, but I do love the elemental chaos. I don’t love the “feywild” (as a name, but even as a concept), but do love fairies. The problems with both are kind of interrelated: both are anti-adventure, in that there isn’t a good story about why you’d go there. Think about it: “Hell” gets an A+ on this score because you go there to screw with Satan. “The Feywild” isn’t nearly as on-point: maybe you’re screwing with a fey lord, maybe you’re hunting displacer beasts, maybe you’re harvesting moon-flowers, and so forth. I mean, I could tell a similar story about Hell (“screwing with a diabolical duke, hunting hell hounds, harvesting larvae, and so forth”) but to me they really do feel different. I think it’s that fairy-land doesn’t have a single flavor. By mashing the two together, we give fairy-land a flavor (unpredictability and danger, a little body-horror, a little fear of insanity and corruption).
But did I invent something new by saying that? To my mind, I didn’t really. Elemental Chaos + Feywild = Faerie, sure, but normal D&D calls that agglomeration Limbo. And you know, I’m totally okay with that? To say that my land of Faerie is a little slice of Limbo, that spells that would use the shadow roads to travel go through the twisting spaces of limbo, that shadow creation and illusion creation uses Limbo? All seems right to me.
Then we get the new-age and atheistic land of the dead. Obviously D&D has the problem of too many death gods: are dead souls bound for a sort of ecumenical heaven, or the well-defined Hell, or Hades, or the Abyss, or what? So of course the only real answer is to define some sort of specific land of the dead, themed in a gothic and dead-lands style, say that that’s where they go, and cut the rest off. These days, we call that place the Shadowfell, but it used to be the negative energy plane — and even before that, it was Hades. So let’s just call it Hades again, perhaps.
And of course, Heaven and Hell. Famously one can reach from Heaven to Hell via vertical movement; doesn’t that mean they’re the same plane? Well, I dunno. Maybe. Maybe not. Let’s go ahead and call them all different places for now. And I’ve loved the idea of the wormworld, a hellscape dominated by the aberrations and where the gith’s drama plays out; I stole Gehenna for its name. So that’s a different place too.
Back to the “ethereal plane”. It links the worlds, and of course all the abyssal demon worlds — the ethereal plane is the same as the Abyss; it’s not a plane which is by its nature evil, so much as a region of space dominated by the demon lords.
Okay, look, here’s the point. There’s a lot of wasted metaphysical space in D&D, and it’s overly structured. The Kingdom of Heaven can easily be a place you can walk to from the Despotry of Hell. It probably even should be, so that there can be places for flights of angels to get into battles with serried ranks of devils.
So: what’s the point of the D&D planes? They’re described as one-note flavors, and so the evils planes are interesting and the good ones are boring. It’s important to me that the planes be generally good for conflict, so obviously the places of Heaven and Hell, even if they are separate planes, should be “near” each other. Obviously the devils that execute the Blood War need to reach the demons; since I put my demons in little half-realities hanging off of the ethereal, the place behind the world is filled with the execution of their war.
So that’s kind of interesting: the ethereal plane is how you get from The World to all the ruined little demiworlds hanging off of it, and the Devils are hegemonizing as many of them as they can, in a process called the Blood War. D&D rationalized!