The colonization of the stratosphere was a singular event that took place in a short burst around ten million years ago.

It was something of a miracle that the stratosphere had been colonized at all. There was a dead zone of eight vertical miles that spanned the tropopause separating the stratos from the T-alphas. Perhaps the frigid temperatures and thick ozone were inimical to mezan biology, or perhaps some historical fluke of migration had simply passed it by. Whatever the reason, this no-man's land played a crucial role in protecting early stratospheric settlements when they were at their most vulnerable.

The first founding was clearly the work of a group, a Mayflower rather than a Marco Polo event. The stratosphere was an arid, desolate place where only the hardiest algae and lichens managed to eke out a mineral-like existence. The limiting factor was water. It was the rare cirrostratus cloud that soared high enough to deposit a sugar-fine layer of ice.

Under these conditions, no single individual could have bootstrapped itself into a technological civilization. Along with numbers, the settlers must have brought along ample supplies of water and edibles. This pointed to the sort of super-dirigibles used for transporting trade goods. It likely drifted off course, suffered a mechanical failure or got caught up in a thermal plume. However it got there, once it landed the crew would have soon collapsed into metamorphic protoplasm.

The big mystery was how the first successful transformation was achieved. The strato-spars were devoid of any life larger than a mite—so where had it gotten its body template from? One theory was that it came from the dirigible shape itself. The rounded chest of a stratomezan was not unlike a tapered blimp. Or maybe it was just the lucky result of a default body-making mode or a random shuffling of parts. But once the first metamorphosed, the others could use it as the template to copy.

It would have been touch and go for decades, maybe centuries, life reduced to a Shackleton existence, a daily fight for survival. Slowly, they would have constructed the first thermal traps, planted the first crops using their own refuse and erected the first fixed structures from the cannibalized materials of the dirigible. Even then, early settlers would have required periodic resupply and an infusion of labor.

Direct relations with the T-alphas was unlikely since they had little to trade and, even if they had airships of their own, couldn't visit without suffering a metamorphic reversion. A better strategy would have been to lure wayward flyers by setting a light in the heavens, a will o' the wisp to entice the curious or desperate. If the airship could be persuaded to land (perhaps with a little help from tethering harpoons), nature would do the rest. Newcomers could be added to their number or just converted directly into food (it was not considered a crime to kill an individual in a protoplasmic state). The population had to be kept in strict balance lest they all starve.

It would have taken tens of thousands of years to build a self-sustaining colony but, perched high atop a diamond pillar where it never rained or snowed or even turned breezy, the stratomezans had all the time in the world. There was little danger of invasion from the T-alphas. So long as they could stay warm and well fed, they could endure indefinitely. The most serious threat to their survival was their own carelessness and over-consumption. As the population approached maximum density, they would have turned their gaze toward the horizon where, on the ever-clear nights, the gleaming spines of distant spars pierced the swirling layers of clouds.