The Shape of the Outer Planes

If you look in the Monster Manual, the letter D chapter is utterly massive. And that's not that strange when you consider the broad categories of creatures that start with D. This letter holds Dragons, after all, with ten color variations and four age-ranges for each color for a total of 40 dragon types (before you even get into variant templates like Dracoliches and Shadow Dragons or lesser dragons like Dragon Turtles.) You also get the two most iconic types of fiends - Devils and Demons.

Fiends make for good villains - after all, they are defined by the fact that they're evil. My basic understanding of fiends is that denizens of the lower planes are, inherently, fiendish. Even beings that one would think would be some other creature type, like Night Hags deviating from their Fey kin or Tiamat, the Goddess of Evil Dragons, turn out to be fiends when they live in the lower planes.

Given that the game's tendency to have heroic figures facing dangerous threats, it makes sense we'd have a larger rogues' gallery of evil creatures. Fighting a fiend never carries much inherent moral complexity given that these creatures are literally an embodiment of evil.

Given D&D's famous alignment system, it also sort of makes sense that the kind of primary combinations of moral/ethical alignment get the most attention amongst the fiends. Devils, being at the direct intersection of lawful and evil, and demons, being at the direct intersection of chaos and evil, are pretty good poster children for how that alignment system works.

Now, we also have other types of fiends. To fill out the ranks, Yugoloths (in earlier editions called simply "Daemons" - I believe that the term Yugoloth was introduced the same time that Devils were renamed Baatrezu and Demons were called Tanar'ri as a concession to the Satanic Panic, though given how similar Daemon and Demon sound and are spelled, it makes sense that they kept the alternate name after those sorts of concerns died down) represent Neutral Evil. But my understanding is that it doesn't quite break down just that simply. After all, there are 7 Lower Planes. The Nine Hells of Baator and the Abyss are the most storied among them, being the planes of Devils and Demons respectively, but I think each actually has its own type of fiend. Yugoloths, for instance, don't live in the dead-center Neutral Evil plane, but instead in the slightly lawful-leaning Gehenna (which is basically between the Nine Hells and Hades.) That leaves Acheron, Carceri, Hades, and Pandemonium without an iconic fiend.

Now, to be fair, Hades does have its Night Hags, but given that there's only a single stat block for such a creature, it's not really the most satisfying.

One question I often have regarding the planes is whether we should be looking at the great wheel as a circle or as a square. Let me explain what I mean by that:

If it's a circle, it means that the "Neutral X" or "X Neutral" planes, namely Mechanus, Hades, Limbo, and Elysium, are actually the most distilled and profound expressions of their main identity. This would make Hades more evil than the Abyss or the Nine Hells.

That doesn't totally feel right - it's hard to imagine that any plane is actually more evil than the Abyss - but the alternative also has some odd consequences:

If it's a "square," you can imagine that Mount Celestia, Arcadia, Mechanus, Acheron, and the Nine Hells are all equally Lawful, and they only differ in degrees of good and evil. This also feels sort of inaccurate as well, as Mechanus seems so much more dedicated to the concept of Law than, say, Mt. Celestia.

Is it possible that we're looking at some other shape? Given that Mechanus and Limbo are neither upper nor lower planes, perhaps they have some special status.

It is also, perhaps, important to think of Neutrality, in these cosmic alignments, as being not a lack of something but a positive, active choice. The existence of the Outlands, for example, in the Planescape setting, suggests that one can pursue neutrality with some level of gusto, rather than simply invoking it as a way not to take a position. This, then, perhaps gives places like Hades or Mechanus a strong identity without taking away from the Nine Hells. Mechanus is a place is emphatically amoral, not moral or immoral. Similarly, Hades emphatically rejects the industrial orderliness of the Hells but also the unpredictable disorder of the Abyss, and as such revels in its Grey-ness (Hades is often called the Grey Wastes.)

However, if we use Neutrality as its own active choice (and even kind of divide it between Moral Neutrality and Ethical Neutrality - sidenote: I'm using "ethical" as shorthand for the Law/Chaos spectrum, even though I think in real-life ethics are a big part of being a good person - but that might just be because I'm a lawful person,) what that does do is that we find a more complex relationship between the sort of "minor" outer planes. By these I mean the ones that are more strongly aligned with one spectrum than the other. For instance, let's look at Ysgard. Existing between Limbo and Arboria, Ysgard can be referred to as either the most chaotic of the upper (good) planes, or it's a chaotic neutral plane with a slight inclination toward good.

But, essentially, it seems that Ysgard is more chaotic than it is good. It's strongly aligned with chaos, but only marginally aligned with good.

Maybe.

Again, it depends on the "shape" of the planes. It's possible that you conceive of every upper plane as being equally good, with just different quotients of law and chaos. Alternatively, everywhere from Bytopia to Gehenna is equally lawful, with just different quotients of good and evil.

But it can't be both.

Because it it was both, then there really wouldn't be any difference between, say, Pandemonium, the Abyss, and Carceri, because all three would be chaotic and evil.

Now, to be clear, the ambiguities here are A: very granular. In the long run, each of these planes just has its own cool flavor that you can play with, and exactly why, for example, something between Neutral Evil and Chaotic Evil is a big prison plane is less an obvious consequence of the alignment as much as it is a cool concept (frankly, I'd probably flip Acheron and Carceri, as a prison seems more lawful than an endlessly raging battlefield), and B: easily explored in-universe by scholars of the multiverse. Fantasy, of course, is distinct from Science Fiction in large part due to the unexplained nature of how things work. Why the planes should take these particular forms is something the players could explore, and indeed, you could have some character theorizing about this "shape of the multiverse" question who sends a high-level party on a fact-finding mission through the outer planes in an attempt to answer those questions.

Taking the DMG's "Building a Multiverse" chapter to heart, my own D&D setting has its own outer planes, though I've been exploring, particularly after seeing how Eberron does its ones, finding new ways to order things - like having an unknown number of outer planes that don't all work quite like the ones in the Great Wheel cosmology. In fact, I began by actually using the 5 colors of magic from Magic: The Gathering (this was before Guildmaster's Guide to Ravnica came out), creating 1- and 2-color planes, though it was relatively easy to plug these into the sixteen slots of the Great Wheel (the Black/Red one, for example, is basically the Abyss with a different name - Tartarus.)