My world was created as a prison for Tiamat after a primordial conflict between the auran gods and Tiamat. Originally, the world was "flat": divided equally between water and air along an infinite plane. The auran gods won the war, and confined water to planet-sized sphere, which is my primary world.

The structure is maintained by four equally spaced pillars (where the corners of a tetrahedron inscribed in the sphere would be): the Pillars of the Sky. They are the Pillar of the Sun, the Pillar of the Earth, the Pillar of Thunder, and the Pillar of Dreams. The first three correspond to the three elements of my physics.

Those three pillars outline what could be considered my material plane. The other three planes of the surface of the sphere could be considered akin to the astral plane, because they are influenced by the Pillar of Dreams. They are the Plane of Night, opposite the Pillar of the Sun; the Plane of Mist, opposite the Pillar of the Earth, and the Plane of Death, opposite the Pillar of Thunder. 

You can reach these planes simply by traveling far enough on the surface of the sphere, but few people have. Things start to get weird when you get close to the boundaries, kind of in a feywild / shadowfell way. You might try to sail to the Plane of Mist, only to find yourself back where you started without ever turning.

The deep ocean is a kind of abyssal plane / plane of water. It is bottomless. It's just saltwater all the way down to the center. Continents just float on top. This is where Tiamat abides, along with lesser chaotic beings.

Above the tops of the pillars is a plane of air / celestial plane, where the auran gods live. There is no "space" per se. It's all filled with air, but gravity starts to run out above the tops of the pillars. You don't necessarily need wings to fly, though of course it helps. Swimming through air by flailing your arms is slow going.

There may, of course, be other spheres of water imprisoning other primordial chaos gods in far-flung regions of the plane of air. And who knows if the plane of air is infinite, or still bounded on one side by some other infinite plane of water, or itself a vast sphere enclosed by an unbounded expanse of water.

The world was first born of water, earth, and sky, with flame seldom seen but still present. All the world was an endless sea, with sky above and earth below. But the four primal gods decided to create the continent of Borrelia, a land above the never-ending sea. This fundamental change to the planet brought forth the genies, the first elementals. But when they decided to create time, there were unexpected consequences. Three new gods were made- one for the sun, one for the moon, and one for the stars and for magic. These gods created a new continent, and, in time, their own race, the elves. The race of gnomes was also born on this strange land beyond the seas of the mortal world. 

Before the fading of the gods, the four elemental planes were home to the gods of their respective elements. Night and day resided in the mortal world, and the stars flew high above it. The numerous other gods that came into being made their homes on various demiplanes, as well as on the lower and upper planes, which are the primordial representations of different moral outlooks. Beyond the mortal plane, there are no certainties. Everything has the possibility to be infinite. Only on the material plane are creatures born, and only on that plane do they die of age. The immortal beings of the outer planes are primal manifestations of their own ideals. They do not change. They are, quite literally, a representation of their beliefs. It is impossible for them to become anything other than what they already are without some outside influence. But mortals, on the other hand, can become anything they wish to be.

In a war some millennia after Tiamat’s imprisonment, the Elder Phoenixes (Sun Phoenix, Thunder Phoenix, and Earth Phoenix) were close to prevailing over Tiamat and destroying her utterly. However, Tiamat managed to kill one and capture another in a surprise turn. As long as there are two Elder Phoenixes of different gender, they can regenerate the third. Tiamat threatened to kill the one in captivity. The Elder Phoenixes agreed to a truce, under the condition that they mate with Tiamat. The offspring of the Sun Phoenix and Tiamat were the humans. The offspring of the Earth Phoenix and Tiamat were the elves. The offspring of the Thunder Phoenix and Tiamat were the aarakocra. The continents of the material plane were created at this time to be their homes: Solasta for the aarakocra, Gord for the elves, and a southern continent for the humans. They were to serve as a kind of wall between the Phoenixes and Tiamat, and the peoples would be its guardians. Tiamat knew the Phoenixes would no longer resort to total war against her, as it would harm the peoples who were their children.

The war between the dragons and giants was full of bloodshed and destruction. Every battle shook the earth and tore the sky. One battle, between an ancient dragon and empyrean, was particularly gruesome. As the dragon slashed at the empyrean, the giants blood streamed into a cave that led deep under the ground. The blood merged with the stone of the cavern, and it came to life, becoming the first dwarves, who were as strong and resilient as the rock from which they had sprung.

The first appearance of the elves was almost a hundred years after the creation of the first dwarves, though the Dragon Wars still waged on. They sailed to Borrelia from across the Western Sea, from a continent hitherto unknown. They were made from the forces of sun, moon, and starlight, and those were their gods. They taught much to the dwarves of magic, and the dwarves taught them of crafting and smithing, which they soon perfected. To this day, they remain the most long-lived and eloquent of all mortal races in Borrelia.

The first humans came into being on the Isle of Wanir, to the northeast of Borrelia. It is believed that they were created by the god Ramsicor, lord of change and innovation. The fighting of the white dragons and frost titans in the north had created so much ice that a bridge had formed between the isle and the mainland, allowing humans to cross over to the Borrelia just over a hundred and fifty years after the arrival of the elves.