Quabra

This one was frustrating, for two reasons. First, because I wrote most of it under... less than ideal conditions. And more interestingly, because of the difference between stories and worldbuilding. If I was writing a story set in Quabra, I probably wouldn't set it 'now'. Actually, I'd probably set it around when Vasi Purogami first set foot on Do, when Akamsa was still on a knife's edge and when fighting phantoms was still mostly a matter of luck.
I went back and forth on whether or not to edit it. I ended up not doing so, on the basis that, honestly, I'd already written it and I haven't had much time today. But also, I tend to think there's an advantage to having a preference for setting these tbings as late in the timeline as remains interesting.
The surface of Quabra is devoid entirely of vegetation. There is only one kind of animal that lives its life on the ground, which itself is cracked and broken. And the reason for that, is the animal that does live there. The ativir, the great beast of Quabra. Even the smallest stands more than a dozen miles tall, and twice as long. One would think so huge a creature must soon die, but the ativiru never ate, or drank or even breathed - if it had not been obvious from their sheer size that the creatures were somehow magical, the briefest observation would have demonstrated that they must be. Not that it was easy to observe one - the only way to get a good look at one would probably have been from another planet.
Noone knows exactly where they came from - save that they came through great glowing portals, which opened suddenly, and closed as fast when the ativiru were through. And even that knowledge has been gained only through extensive divination. Anyone who might have been close enough to have had firsthand knowledge, had not survived their arrival.
For it was not that the beasts attacked people. Nor, indeed, had they even stepped on any - they hadn’t got close enough. For the impact of their feet on the ground was by itself enough to kill anything for miles around.
The ativiru were slow, for their size, but they still walked far faster than a human could run or drive. There was nowhere to run, they strode through even the deepest oceans as though they were nothing. It was possible to avoid them, but you had to be fast, smart, and above all you had to be incredibly lucky.
Then, there were the phantoms. There had always been a few, floating around but now they were everywhere. And they had started attacking people, which was the last thing anyone needed.
Over time, food got harder and harder to come by, and more and more people got unlucky. Until humanity was just a few isolated pockets, each one not sure if it was the last one.
In one of these pockets, there happened to be a man and a woman. The man was named Nayak. And he is credited with having suggested the obvious - living on top of the ativiru. It wasn’t the idea, though, for which he is mostly remembered, but as a leader. He organised the survivors, to make or scavenge or conjure what they would need. Soil, seeds, water, what food was left… all the things they’d absolutely need to survive. And then, they built great envelopes, to haul the whole thing up. The project took years. But eventually, it was complete - a great vessel which would carry, as far as they could tell, the whole of what now remained of humanity.
And this is where the woman came in. Her name was Daya, and she is remembered as the greatest mage in history for her part.
 First, she called up a swift wind, to take the vessel towards the closest of the As the great vessel rose, it became cold, and hard to breathe. The vessel rose slower, and slower. But Daya called upon his magic, and wrapped them in warm air.
And so they rose, and rose, higher and higher, far higher than anyone had ever flown. It seemed to take an eternity to reach the bottom of the creature’s torso, then an eternity more to reach the top.
As it turned out, the creature had a broad, flat shell, covered in great spines. They would soon learn that the shell made an excellent building material.
The first thing, though, was to make sure they would survive the night. And this is the feat for which Daya is remembered. For she cast a new spell, and bound it into one of the shell’s spines (it’s said that it turned to diamond that very instant, though that was probably actually done deliberately some time later). It was, in essence, the same spell she had cast before, to make for them a pocket of warm air. Except this spell didn’t cover only a single vessel, but the entire shell of the ativir. And that is how Akamsa was founded.
There were few enough people around then that now, generations later, their numbers have only started to recover.
Over time, as the population grew and Akamsa became established, new sky-ships were built, and sent out to colonise new ativiru. Each one carried numerous magi, to replicate Daya’s spell.
It might seem odd, to have expanded when so much space was left for Akamsa to grow. But there were reasons - from political dissent, to the simple grudges that can develop over the centuries. But in truth, the real reason was that everyone was very aware how close they had come to extinction. All staying in one place simply didn’t feel safe.
Today, four of the ativiru have settlements on them.
Ek
The first of the ativiru to be colonised was named ‘Ek’ by the settlers. The city of Akamsa is the heart of what remains of civilization, though even it is still, by the standards of the old world, barely more than a small town, surrounded by fields. Trade happens between the other three settlements, mostly goes through Akamsa.
Do
The second was named ‘Do’. The original colonists were in large part political dissidents and risk takers, and the fingerprints of that history can be found in their culture to this day. Traditionally, those who go to the surface come mostly from ‘Do’, and something of a feud exists between the people of ‘Do’ and those of ‘Ek’.
Tin
‘Tin’ is known mostly for being insular. Its foreign policy consists primarily of trying to keep a balance between ‘Ek’ and ‘Do’. They are also known for learning - they have the largest library remaining in the world, and the only university. It is Tin where people go who wish to become magi.
Car
‘Car’ is a fairly new colony, containing only a few hundred people. It hasn’t developed much of a reputation yet, and still relies upon the other colonies for support, and each is eager to leave its own mark on ‘Car’.
Despite their differences, the colonies have more in common, than they do that sets them apart. Each one is a dictatorship, each is primarily agrarian, and deals with criminals by casting them over the edge.
Beyond the obvious difficulties of political conflict and a barely sustainable population, there is one more problem that must be faced by the colonies, and that is that they are not entirely self-sustaining. Sky-ships must, from time to time make the long, perilous journey from the ()’s back, down to the world below, and fend off the diverse phantoms that inhabit it, to gather the raw goods they need. In the case of more basic things like stone and water, this not difficult - they can be gathered and loaded quickly. But as more and more infrastructure is rebuilt, there is more and more demand for rarer and rarer materials, and so the expeditions have to spend more and more time on the surface. In places, mines have even been set up, the crews digging as deeply as they can, before the approach of an ativir forces them to escape back into the sky.