What is your setting's cosmology?

...

A combination of infinite improbability and many worlds interpretation of quantum mechanics. Basically there is nigh infinite amount of universes but physical laws are not 'laws', they look like laws because by sheer random chance particles behave as if they were affected by laws. If they don't even for a moment life or anything material ceases to exist in that universe. Thus you think there are laws because you can't exist where the laws don't work. Due to that almost all of those bubble universes are weird messes of elementary particles constantly changing and shifting while the tiny but still numerically huge amount of habitable universes can have any physical law needed by the plot.

standard DnD world set up with the "planes" renamed. everything is connected though, no planes bullshit. so, that means if you want. you can just walk to Inferno (hell) and the FeyFell (feywild),

Modified Planescape

The first iteration of the world was a standard universe similar to ours, with the exception that stars were sapient, and were a source of magic.

After human life grew, and belief gave birth to gods, it wasn't long before the "old gods" that were the stars and the new gods of men fought.

Their struggles decimated the numbers of each, and tore reality asunder.

The entirety of the universe was going to collapse into nothingness, so the gods rallied together and shaped a patchwork world over the pieces.

The new world is a world not of matter, but of concepts and ideas. The waking dream is a Geocentric universe, with what few stars remain orbiting around the world, with the sun and moon.

The inner section of the world is hollow, and the interior surface is bathed in the green light of the inner fire, a portal to the rest of the multiverse.

There is no chemistry, no elements, no F=ma or anything like that. Some properties behave analogously, but the substance of the universe is inherently one of ideas.

As people live and die on the planet, the gods slowly harvest excess energy to repair the physical nature of the previous universe.

reworked World Axis.
Basically the Axis is unchaged but while creating the world, pieces of Ao's body broke off. Ao created the Axis and sealed it off, nothing existed outside of Axis but pieces of Ao's presence. Simply while Manual of Planes is inside World Axis sphere. Outside of the sphere pieces of Ao became sentient and gods themselves, none as powerfull as Ao, but more powerfull than any of Faerun gods.
There are ten "good" and ten "evil" (i dont like calling tchem good and evil but it's a simplification) gods and countless others, less powerfull dietes. All those beings started creating their own worlds, as countless as Planes within Axis, those worlds orbit the Axis which serves as sun.
There are different kinds of worlds, spheres, planes, finite in volume but infinite in area, moebius strips etc.
The Worlds outside of World Axis are called Eclipsed Planes (by inhabitants of Axis who know of tchem), because their view is eclipsed by elemental chaos and astral sea.
Knowledge of Eclipsed Planes is not common among inhabitants as knowledge how the axis is build is not common in Eclipsed Planes.
additionally, inhabitants of Eclipsed Planes cannot enter Axis without invitation.
Inhabitants of Axis are natural to it and can travel Planes without problems but outsiders must be first invited to Sigil, from where you can travel anywhere. Even if you were invited already, if you want to travel from Eclipsed to Axis, you must go through Sigil, unless you are exceptionally skilled magic user.
there is a secret socjety responsible for Invitations to Sigil but i won't go in too much detail here, unless you want to?
Far Realm is also present, it was created when Ao threw out his fears to begin crafting the Axis. Those fears also became sentient and created outer layer of Universe.
So there are 3 basic layers: the Worlds Axis, which is the core, then Eclipsed Worlds, then Far Realm.
1/2

2/3
for how the universe is build that;s basically it but Magic and Psionics are connected to cosmology.
Magic comes from Axis, is created by Ao's presence and acces to it is controlled by Ao but pure magic is so potent that it seeps through the barier of Axis.
Psionics is similar but it comes from Far Realm.
without Ao's control over Magic of Far Realms control over Psionics those powers are much more powerful and potent in Eclipsed Planes.
If A Plane is close to Axis, then Magic is more potent than Psionics and vice versa. Important thing is that potency of magic/psionics does not correlate to numer of magic/psionics users and world's attitude towards them. for example the world there my current campaign is set is kinda in the middle between Axis and Far Realm but still close to Axis. Magic users are rare, with wizardry taking many years to study and requiring natural talents, in the world of around bilion sentint beings there is around 10;000 full fledged wizards (well, iclunding students at magic academies) and around triple that tricsters, small village mages etc, who know a few spells, nothing more. (bards do not count into it as bardic powers are like being a sorcerer, its a natural gift), Sorceres are very rare and very valuable but in some countries they are forced to undergo formal education. But with magic being hard to learn and master it's really powerfull, if you have talent and determination, in worlds history one mage put a whole nation to sleep with one spell for his king to win a war and another build entire city of stone and steel, creating the materials from thin air, not reshaping the landscape but that level of power is incredibly rare and usually magic users of that tier are distant to mortal problems or more commonly are hard to find elves consumed by their studies in their forest homes.

As for Psionics in this world. it was anomaly until Far Realm attacked the World, the World defended itself but on Island is stil unhabitable. Since then Psions are persecuted and killed on the spot BUT it's really easy to lern basic psionic powers, so some people risk it for example but usually it many tries and months to learn simple powers, not to mention advanced ones. There are also talented individuals who are much more powerfull in psionics. there is a nation of Psion Githzerai, this race is naturally talented, but not very powerfull in using it, so almost all of Gith know psionics but only few are powerfull.
Power of Mage/Psion on any plane is dependent on where was he born, not where he is, as power is stored withing accesories or ones body/mind, so powerfull psion from world near Far Realm willl not be weaker in Axis where psions are born very weak

Pretty normal big bang, except that gigantic space whales have appeared within the space dust and begun to interact with the celestial bodies. Their conflicts and cooperations, since their thoughts are the stuff all magic is made from, have in the end created life.
On the planet on which the adventures are set, some whales have settled down in the oceans, others have adapted to live in gigantic forests their mind have created. In the middle of these two camps, humans, animals, and a very particular set of beings have appeared because of the conflict between the two camps. Some of these living beings are made insanely powerful in order to keep the Beasts and the Whales from meeting again, since none of them want to stop experiencing life in these two environments yet.

I use the ptolemaic cosmic model with the stars as gods. The world was once a sphere but after an event near the dawn if time it took the form of two hemispheres. Places you could call planes exist, specifically a world were only a single sun shines in the sky and never moves, a place where the sky us empty and the land has no plants or animals (elves think this place is the end of time), a mirrored world which no one gas discovered or explored yet and an infinite stack of subjective dream worlds that get more divorced from reality the deeper you sleep. That last one in actively patrolled by various dreaming agents and spies as having a communal dreamworld (the lower dream levels match up 1:1 with the waking world) makes it easy for conspiritors to meet in secret.

No elemental planes though. Those are trash.

Dirt spheres revolving around incandescent balls of plasma.
The dirt spheres are full of dead gods.

So... like rolling a billion dice, all the universes that don't have a billion 6s would be uninhabitable, but you roll them constantly, so the only universe that can have life would be one that happens to get a billion 6s every role?

Kinda like but still fairly different.

There is the "World" and there are locations in it that strange and mystical beings and monsters can slip through into the World. The realms the majority of these things come from are known as the Dreadlands and Faerie Kingdoms.

Now, not all monsters or otherwise come from them, oh no! some come the depths of Chaos, a twisting realm where water burns, earth floats and more. Here the Demons and other foul beasts and monsters reside.

Opposite Chaos is the realm of the gods, the Joyous Realms. Now herein lies some issues because there are evil beings and gods that live in the Joyous Realms just as there are goodly beings in Chaos. The differences are often minor and usually overlooked by the common person though the stories still tell of these beings like the trickster god who goes freely between all of the realms sowing chaos or assisting people at a whim but whose "home" is in the Joyous Realms.

How this came to be is known only to the Gods and their respective counterparts in Chaos and they are loathe to share their secrets with mere mortals or even their closest attendants.

I shamelessly stole this from another thread on Veeky Forums about a year ago. If the original poster sees this, thanks, my dude.

Before existence existed, there were two brothers - Creation, and Preservation. Anything that comes to be, and anything that still is, is from these. For the first eternity of eternities, they lived in solitude.
But they wished to share existence with others, so they built for themselves a Thousand Thousand sons. And for an eternity, everything was good.

One day, Creation looked upon Preservation and said "I do not need to make any goodness for him. Any he needs, he can simply preserve!", and so Creation turned a blind eye to Preservation, and the goodness that was within him began to be destroyed.
In turn, Preservation looked upon Creation and said "I do not need to preserve the goodness in him. Any goodness he needs, he shall create!", so Preservation turned a blind eye to Creation, and the goodness that was within him began to be transformed. This is the origin of all evils in our world.

Eventually, the two brothers grew tired of their Thousand Thousand sons, and desired a new world. So they tore the hearts out of their sons to build this world, and tore out their ribs to cage off this new world from the Thousand Thousand. On this world, they built the gods - powerful beings able to shape the new world to their desire. The first of these, born as a mediary between the Gods and their two fathers, saw the Thousand Thousand above him, gnashing on their own bones, tearing at the cage to return themselves to their hearts, and he grew fearful of his fathers. So he burned the eyes of his siblings, so that they might not see the pain above them, but glimmers in the distance; and burned their ears so that they might not hear the screams of the Thousand Thousand, but mere wind. And so he retreated away from the world, and has not been seen since.
[Cont]

The world is both flat and infinite. Gods exist in a parallel plain and can peer into the mortal realm with great effort. They develop interests in aspects of the mortal world basically because they're just so bored.

And thus the primordial brothers, the fathers of gods, turned away from their offspring. They neither shunned them that they should be destroyed and transformed, nor showed them joy that they might see creation unfold and be preserved.

As the Thousand Thousand took in a breath, their ribs expanded. In this expanse pooled blood, and the gods built for themselves their own worlds, suspended in blood. These are the great planes of the gods.
As the Thousand Thousand continued breathing in, their bile pooled into the new expanse, and suspended in this, the lesser gods and demi gods built their lesser planes. The breath continued, and in pooled the phlegm of the Thousand Thousand, and in a bubble of this is where our earth is suspended, and another bubble is the sun; and another bubble, the moons; and each another, the planets - our guardians.
Our world, and perhaps all worlds, is made of two hemispheres, exactly reflected in each other. The material - made of all physical objects, all matter, but inert, and; the spiritual - land of our souls and all movement, all energy. It is the interaction of these two worlds, a cosmic symbiosis, that we see in our world.

This is the nature and order of our world, and of all worlds.

A flat world with most of the surface area occupied by a world sized tree.
Roots on the surface make up the mountains, whilst roots underground seep to the deepest foundations of creation. A trunk so tall and wide that a single lifetime is not enough to see all of it. Branches blanket the sky and breach through the firmament. Vast forests grow along all parts of the tree, sustained by the internal rivers running within, and great lakes formed in ancient hollows.
There is no night or day, for the sun spirals around the tree, casting it's great shadow over world. The moon stays still in the sky, entangled in the tallest tendrils.

>unironically using a worldtree

>not using a worldtree

>m-muh wurrrld trie
This is something uncreative hacks use in place of a regular world because they think ripping off norse mythology makes their setting complex

I dig it.

>using a female force tree to explain how rey kenobi can kill emperor snoke and kylo ren solo

>implying only norse mythology uses trees
Look at the image I posted. There's a reason trees are powerful symbols.

everyone gives a different answer
the true answer is that it's made of a .pdn world map and bunch of .txt-s describing stuff

everyone in setting, that is

Short version:
In the beginning there was an infinite void. Perfect entropy and undulating nothingness. The fun thing about infinite chaos is that anything can happen with enough time, so like monkeys with typewriters, the spark of law came to be. A single spotlight in the endless abyss. Like a single eye, it's sight radiated out and placed judgement on what it saw. The void shirked the light, and from this came the first creations. Simple shapes that held form for more than a moment, a first. The light, thrilled with the order it imposed created more. And then more. And then more still. Nothing more than a child playing with blocks, but it was order imposed on disorder. Unfortunatly the light's own creations blocked its sight, allowing the void to creep ever closer. Corrupting and decaying wherever it could, until the light touched once more.

Each time the light's focus would shift, its old work would be consumed and fall to the void. Eons of this dance, the light would grow and build. Creating worlds upon worlds of majesty in time, only to have them swiftly consumed. Incredible as it's light was, it could not create in such a way as to stave off the void from all sides. It had grown so much, incomprehensibly big, and yet still the void stretched outwards. From this frustration, the light shattered itself, forming every star in the sky. Billions of trillions of points of light, to cut through the void from every angle. Each star a god in their own right. Each an aspect that would create and build worlds in their own image, while giving watch to their brethren's worlds where they could not peer.

This still was not yet enough. Even then, shadows could still be found on every world. Beings of the void would congeal in every conceivable nook and crack, so a final split was made. Each star split itself off a final time, just a piece. Dim enough that it would flicker and die to the darkness, but bright enough that it could repel. This became the first mortal life. 1/2

Generic as fuck, but I like to think I've fleshed it out enough to make it interesting even without an innovative concept basis.

You have six elemental planes (fire, water, earth, air, dark, light), alongside Creation, which acts as a nexus and has the highest total area of any world, the Abyss, an artificial territory designed as both a prison and a means to purge the emotion from the restless consciousness of the deceased, the Soulsea, a natural 'cloud' of vital energy which cycles 'souls' into and out of the world, and the Mists, which is where spirits go after they pass through the Abyss. (Spirits =/= Souls in this setting. The Soul is just a coherent mote of vital energy. The spirit is the consciousness which exists beyond flesh and soul. A being needs all three to be sapient and 'healthy', though there are exceptions.)

The six elemental planes are seas of chaotic, aspected energy. 'Islands' exist in these seas, which act as sub-planes, known as Houses. Each House contains Thrones. New Houses are born and old Houses can die or get lost within the planes, and Thrones can be built and torn down, as well. Each House has it's own geography, climate, flora and fauna, though they tend to align towards their element. You won't find an arctic sea in a House of Fire, for example, or if you do you need to leave because it would take enormous amounts of power to stop it dissolving immediately.

Beings who hold Thrones are referred to as Empyreans, and are effectively the divinity of the setting. Of these, there exist three categories: Risarians, the primordial beings who have always existed, few in number, inscrutable, and great in power. Neorim, Empyreans who spawn from chance alignments of motes within the Soulsea and became 'heavy' enough to 'fall' into the Planes. Ascendants, mortal beings who, by accretion, by gathering the threads of fate to themselves and generally being metaphysically 'bigger' than other mortals, transcend their mortal vessel.

God aren't real but magic is; magic is fueled subconsciously as much as consciously so if a paladin believes he has divine power it'll manifest as such. I suppose if enough people believe that the Dwarven God Balik will show up in battle their collective will will make him.

Running theme I'm playing with is that Gods are what you make them, and anything can be a God is someone believes.

Each House has at least a Lord. There are a myriad of minor Houses which are generally no larger than a few square miles, which only have a single Throne. Most are obscure and keep to themselves, unwilling to get involved in Empyrean Politicking. The largest House of each elemental Plane takes the namesake of that Plane, and becomes a High House. There are about six High Houses which do not fit into any particular Plane but are instead held in balance by the power of their Risarian Lords. These are High House Death, High House Life, High House Time, High House Abyss (Plot!), High House Shadow, High House Blood.

There are about a half dozen major Houses, with at least five Thrones, for each Plane, and these are subject to constant internal and external bickering.

This entire Planar Landscape was, until recently, mostly cut off from Creation by way of a Ward cast by the traumatised survivors of a crusade against the Planes which resulted in the extinction of hundreds of intelligent races, and the reduction of hundreds of Empyreans into little more than fragmented sparks of power with no will to act on their own. Now, though, that Ward has been broken, and the Empyreans have started to meddle with Creation again, establishing cults and bargaining with mortals rather than attempting to control them through sheer force of will, which was what prompted the crusade.

Empyreans cannot truly die. They can be reduced to sparks, though, which can be (temporarily, like clipping something to your being) absorbed and utilised by any mortal with enough power to wield them effectively, granting a measure of that Empyrean's original power and portfolio. These sparks also project a copy of the Empyreans personality into the wielder, acting as a sort of internal voice, with access to the wielder's memories. An Empyrean can be restored to it's original state only through the gradual (Millenia-long) process of skimming excess energy generated by the mortal who wields it.

2/2
Mortal life created the final puzzle piece, allowing for millions of tiny points of light to ignite the infinite worlds, starving the darkness of footholds. Each light growing and making more.

Fast forward and head to the world the game is set on, through a series of cataclysmic wars caused by the mortals on the planet, the void had gotten a foothold. Rather than let his creation be corrupted, their main god was about to basically do a factory restore. Where ever their god could not peer was still too steeped in shadow for it's brethren to expunge the growing cancer.

The warring factions each developed a plan to save their world, while crushing their enemy. Both crafting a false god in their image, born from the sacrificed lives of their foes.

The final battles were of such intensity, that the crust of the planet itself shattered, continental plates breaking free from the mantel. In the after math both gods were born, mockery's of their designer's goals. One born to preserve and create life, the other to protect against death. In the shock of their birth they began their own war, pulling much of the planet's surface with them as they rose to take their place in the sky. Each creating their own domain, a miniature Dyson sphere where their rule was law alone. Their power still radiates to this day, as the twin moons. (Feywild and Shadowfell analogues)

It's now a few millennia latter, the world is still recovering. All mortal life resides above the fog, the thick miasma of death that clings to the surface. An unobtainium like magical resource permeates the ground allowing it to float above, creating flying islands.

And that's about it.

The actual setting is firmly rooted in realism. There are two inhabitable planets in the solar system, and the highest of castes travel between them, while the majority of the populus only knows of their world.
Due to some of these populations being isolated for a long time, many mythologies arose. An Islandbound nation claims that their island is the pupil of a godly Sunfish, with the Iris being the surrounding ocean, and the night sky being the lowered eyelid. Another claims that their nation trapped near an oasis in a seemingly endless desert is one of very few civilized settlements inside of a gargantuan hourglass, and that the apocalyptic event of the sand running out and the universe starting anew by the hourglass turning over is imminent.

Also, the magic in this setting is technology the people don't understand.

Four nested Spheres:
1. Sphere: Material world, home of humans, elves, dwarves, orks and vahgai.
2. Sphere: Afterlife. This is where souls go after their death. Surrounds the 1.
3. Sphere: Realm of the Gods. This is where the gods live, watch over the souls and protect the first two spheres from
4. Sphere: Hell. Realm of demons and the 4 Demon Princes. Constantly try to enter the first sphere but are stopped by the Gods.

Essentially this, but on steroids and per every subatomic interaction. Habitable universes are so rare they are below statistical error.

I like it. May steal aspects of it for my next game.

The entire world is the construction of an immensely powerful Black Dragon who goes by the name Garamond. He assembled 8 great artifacts based on the schools of magic and sealed them together with a keystone to create the plane. The denizens of the world call them the Spokes of the World Wheel, and they each carry immense power when used by a talented spellcaster.

Many centuries after the creation of the plane, Garamond's mate Tiamat rebelled against him. She had grown to love the races she nurtured in the world, and Garamond's callousness towards them hurt her deeply enough that she contrived to lock him out. While he was away in the Astral she shut off the plane from all others, locking it away in a fold of space-time. Then she broke the keystone so Garamond's followers could never bring him back.

However, a great war erupted some 200-400 years ago that changed the balance of the realms. The great nations of the world waged a fierce and horrific war against each other using the power of the Spokes, believing them to be little more than magical artifacts. The ancient Elves, in their hubris, decided to end the war with a show of force that would cow all other nations into surrender. They overchanneled the Spoke of Evocation, around which they had built their kingdom, and erased entire nations from the world. However, their reckless use of magic caused the Spoke to weaken, and as they finished their spell it detonated in an explosion so powerful that it fractured the plane itself.

That crack has propagated into many fine-threaded tears in the world through which the Shadow of the Dragon creeps into the waking world.

Overall it's post-magical-apocalypse high fantasy, where the opening to the outside universe has allowed people to access beneficial divine magic but is also heralding the return of the plane's creator, who is not happy about what has happened in his absence.