Bubbles in the Dark is a world written by Enneth. She considers it one of her better works.
In comparison to Avishraa or Earth, Bubbles is a dead world. Its surface is cold and dry and airless, composed of rock and dust. Of its two suns, the closer is is bright but tiny, only slightly distinguishable from the innumerable stars except that it remains fixed in the sky; the more distant sun, slightly orangish in color, moves around the sky only slowly, over more than a cycle. There are vast basins that might have once been oceans, tree-like patterns of trenches that might have once held rivers, but if there truly was an era when the surface was as lively as that of our own world, it is long in the past; the most common disturbances of the surface are the occasional impacts, and the craters they leave.
But here and there on the surface - emerging from deep drifts of dust, or covering over the smaller craters like domes, or filling the entrance to some cave - there is a transparent, if somewhat milky, bubble. These are but the topmost portions of a subterranean ecosystem that clings stubbornly to life, the last remnant of what was once a far greater ecosphere. The bubbles are fungi, or rather portions thereof, the greater whole of which serves as the basis for a precariously self-sustaining colony organism.
The fungi are extremely slow-living, and slow-growing, organisms that eat their way through dust and rock in search of water deposits, which they absorb and store inside themselves. But only the smallest of the fungi can meet their needs solely through water and lithovory, and the larger, more successful ones derive their energy from decomposition of organic matter. Since other lifeforms cannot survive unprotected, the only safe place for them is inside the fungi themselves, and each fungus is a living ark, with whole ecosystems thriving inside their bodies.
Most of the space for these ecosystems takes place inside the bubbles, each one a balloonlike sac inflated with oxygen. These are only possible in a space that is not overly restricted, and the size possible is determined by the limits of that space; sacs growing in cavities in the rock will fill the cavities; those in craters will reach a diameter no larger than that of the crater. Those growing out of the dust, or unprotected on the surface, tend to reach a limit imposed by the metabolism of the fungus and the ability of the bubble to remain inflated under its own weight; this is approximately 100-150 meters.
The bubbles are connected through long, hollow hyphae winding their way through the rock; water and nutrients are transported through the walls of the hyphae between the bubbles and the storage bodies far underground. Through the hyphae, plants and animals living inside the fungus can travel between bubbles, in which water and organic matter tend to accumulate (though some organisms have adapted specifically to living in the stalks). Since the reproduction method of the fungi involved joining hyphae, over long periods the extended ecosystems inhabiting different fungi may have opportunities to mix and migrate.
The insides of the bubbles, at least on the side of the planet currently facing the orange sun, tend to be covered with mats of vegetation trying to take advantage of the meager sunlight; but provided they can be cleared - or are on the nightside, where the vegetation tends to go dormant and die back - they afford an unrivaled view of the surface of the planet, and of the stars above. While of no consequence to a fungus' internal ecosystem, it is this property which caused Enneth to write the Book of Bubbles in the Dark and to set up her own private sanctuary there, in the wall of one of the crater-bubbles. The same property, when Enneth - possibly unwisely - mentioned it to Dlyss, convinced the latter to command her to write her her own spot on the same planet. Unbeknownst to Dlyss, the sanctuary Enneth designed for her is much smaller and more spartan than Enneth's own, thought Dlyss appears to enjoy the solitude nonetheless. Dlyss does not know about the existence of Enneth's own sanctuary, which is located far enough away from Dlyss' that the latter cannot easily teleport to it, nor see it in her visions.