A Diagrammatic Examination of the Great Wheel

See this incomprehensible collection of squiggles above? That is how it All works. Let me explain:

The Wheel Turns, The High Are Brought Low, The Fallen Rise Again

So first: from the outer planes to the astral plane come the basic conceptual building blocks of the cosmos. Not good and evil, right and wrong, pure and simple and straight from the tap, but rather the necessary factors for those things to exist.

Think of it like the Goldilocks zone around a star. For life to exist you need a certain range of temperatures, a minimum amount of water, insolation, protection from meteorites and high-energy radiation, and so on. For any particular Order to exist, you need legibility, rationality, stability, etc.That sort of stuff comes from Mechanus and its cluster of fellow-planes. From the Grey Waste comes despair, from Pandemonium delusion and paranoia, from Bytopia love, and around the Wheel it goes just like that. The outer planes don't provide any single system of Order or Chaos, Good or Evil themselves - Mount Celestia doesn't say "maximize your utility" or "obey the categorical imperative" (at least it's not supposed to). Those emerge later. As well, these outer planes' emanations can be twisted from their original purpose - both by those merely affected by them and by the beings spawned from the outer planes' very essence - love can become abusive control, or stalking obsession, and despair can be overcome and leave you stronger for it. That's how some angels can be dicks and some demons redeemed.

When these conceptual emanations leak into the astral plane, they calve off from the universal wellsprings of their parent-planes, like icebergs from a polar ice cap, and become particular, distinct manifestations. At the lowest levels, these manifestations might simply appear as background characters or themes in mortal dreams, or as flights of fancy in waking minds. These manifestations can also find context in each other, merge, and grow more complex. When these greater manifestations become self-aware they are called gods. It's in the astral that love becomes Eros, or Aphrodite Ourania, that war becomes Heironeous, or Hextor.

A god that remains in the astral alone is latent, a sign unwitnessed, and few of their station can be satisfied with that. They find expression in the material plane, in the transmutation from concept to creation. To do this their power must pass through the inner planes of elements and energies. Your can think of these inner planes of positive and negative, fire, earth, air, and water, as the palette of the gods, to be mixed and applied by their miracles to the canvas of the material plane.

Elementals most often take humanoid form, because these days most gods are humanoid, and their power is one side of the process that gives the raw energies of the elemental planes structure. At the far reaches of the elemental planes you might encounter elementals of reptilian, molluscoid, or stranger form, living fossils of eons past.

On the material plane the Great Wheel earns its name. It is not a simple waterfall torrenting from the outer planes on down, but a cycle. In return for their miracles, mortals grant the gods regalia, demenses, and legions for their naked symbolism, through worship, theology, philosophizing, and propitiation. When they pass from the material plane, mortal souls are drawn to the outer planes that match their nature, expanding those planes' universal conceptions further through the unique particularities of their being and experience.

The plane of shadows is, more appropriately, the shadow plane - it is literally the shadow cast by the material, the existential umbra created left by its interchange of essences and energies with the other planes. Through it, uncountable other material planes can be accessed, though it's often claimed that these are worldly penumbras, only inferior copies of the one true material plane.

Enlightenment

Spend enough time meditating, or take a big enough dose of psychedelics, or walk until all worlds fall away, and you see the Big Picture. That's enlightenment. Problem is, there's lots of ways to see the Big Picture, and so enlightenment brings us no closer to universal harmony.

Proponents of Order see the Great Wheel from above, a perfect circle perfectly divided into perfect components all perfectly balanced to do... whatever it is the Wheel is supposed to do:

Yuan-ti see the same view, but they interpret it as a Great Serpent biting its own tail, being born in death.

Some few heresiarchs see it as a vast eye staring back at them, and are driven to cosmic violence by its glare, determined to destroy everything before it can get them.

Agents of Chaos see the Big Picture too, but they don't even look towards the Great Wheel. They look beyond it, to true Chaos, the absolutely unspeakable and incomprehensible howling void. Chaos doesn't get a diagram - Chaos can't be diagrammed.

Sword-saints - because of course you must be enlightened to become a sword-saint - see the wheel turned on its side, the most terrible of all blades, endlessly slashing:

Disciples of the Elder Evils see the Wheel laid flat on its side, a platter serving up the whole of creation to their masters:

It's said that the greatest of both saints and sinners see the Wheel turned upright, a cosmic "I". Whether they interpret that "I" as a solipsistic reflection of themself in the universe or as a sign of ultimate oneness between all beings is believed to determine whether they turn to good or evil, though the truth is always more complicated.