Cortorq

There is a settlement, a city-state if only it had more inhabitants, that has been built within the Twisting Heart of the Underdark. This strange place is a hollow, constantly turning sphere of rock and metal, orbiting a glob of pure magic: the Nucleus. Some people believe it to be the heart of a god of change. It burns with bright light and enough warmth to give the sphere a pleasant climate, even though it sometimes sparks out with a rain of sharp crystal shards.

The city of Cortorq is built on the inside of the sphere, because the outside has merely a few centimeters of space after eons of erosion, the surface grinding against the endless rock of the rest of the Underdark. The tunnels that reach the edge of the sphere, sometimes align with gateways into the centre of the sphere, for just a few minutes a day. The streets and houses of Cortorq get constant light from the Nucleus, but because the foundation of the town shifts in an endless cycle around the Nucleus, the direction of gravity constantly shifts at a slow pace. Any flying humanoid finds themselves nauseated and unable to keep themselves in the air for long, so only walking humanoids have made their home here.

But why would anyone choose to live in such a disorienting and isolated place? The answer is quite simple and very common: there are unique resources that can be obtained here. The magically charged crystal rain from the Nucleus has reacted with the inside of the sphere to create a landscape rife with rare metals and minerals. Not to mention the magical potency of nearly everything within the sphere. Mages have found their powers amplified by merely breathing the very air there. So of course people have explored and settled here. But they had to be creative to deal with the fact that half of the time, their world is turned upside down.

The streeds are rarely on the inner surface of the sphere, instead being sturdy cable bridges hovering a few meters above it. When the city is inverted, these rope bridges have turned with it, so they are oriented the right way up most of the time. When the sphere has turned in such a way that the bridge has become vertical, there are pulley systems that people can use to lift themselves up or descend. The bridge itself can also be climbed, by the more nimble and daring denizens. The houses and buildings tend to be shaped like dodecahedrons, to have something similar to a flat surface any time of the day, and the sparse furniture is light and mobile, allowing it to be moved with the turning of the sphere. Most beds are usually rotating hammocks, or placed in alcoves with belts holding the sleeper in place. Many surfaces are covered with handholds and foot nooks, as well as leather bumpers, so people can quickly find their way to the "ground" in any place they enter. Either by falling or by climbing there.

Of course, these are the more mundane adaptations. Most denizens have taken to drinking potions of spider climbing on a regular basis, and are therefore able to move more freely and comfortably through the city. This has led to one of the most remarkable feats of engineering in this city: the warding. It is a grand network of magical netting, that forms a safety barrier between the inner surface of the sphere and the Nucleus. This was quickly designed after a tragic incident where a citizen of Cortorq accidentally lost the potency of their spider climbing, at the height of the day. They fell straight down into the Nucleus, perishing instantly and triggering a spark storm that lasted for three rotations. Now, anybody falling off the city would be caught by the nets.