Setting: Dead End Darkness
Imagine an O'Neill cylinder, two thousand kilometres in diameter and many, many times that in length. There are no windows. What is beyond its volume is unknown. A sun moves along its central axis a few kilometres a year. Beneath it is verdant summer; Ahead it is spring, where agriculture is possible and colonies are planted; then dawnwinter for the surveyors and delvers. Beyond that is a vast extent of gloaming, the sun very far away, red and tilted. Mountains cast vast regions into icy shadow. Glaciers dominate. Beyond even this is a darkness that goes on, and on, and on. The same pattern is mirrored behind it. Doomed cities, populations ever less, failing and abandoned fields, fortresses emptied or demolished, and monuments left behind before the ice comes to cover all.
Civilisations creep along, putting out forts and colonies ahead and having their capitals in summer, eventually abandoning them and moving house farther ahead. The process takes centuries. Technology is roughly early modern: Good seafaring with wind and wood, developed optics, obsessive archaeology and linguistics, for these are not the first civilisations to move this way, and from beneath the ice emerges caches, dead cities, tombs, and most precious of all maps and intelligence of the plants and animals of biomes that lie dormant awaiting the light. To ingest this information is a matter of survival in a game played in the centuries to come. What routes to secure for, what to negotiate away to others, what passes or sites to secure at all costs, what dangers overt or hidden to avoid, when to brave the cold and dark to establish far fortresses that will pay dividends decades later, where to allocate survey and delver crews. When to abandon old continents.
Multiple strata are buried. The paths of different civilisations passing this way in different freeze-thaw cycles can be observed. Progression is always in one direction: Forward. But new and worrying information, guarded with utmost care, has been translated from a cache in a burned-layer in the Mid Gloaming. Further progression will reveal the later findings of this long finished civilisation, giving detail to this first discovery, but even what little you know requires deep consideration.
The tablets speak to an end to the long journey of your sun, and a scribe ten thousand years dust names the fate of his world and of yours: Dead End Darkness.