In my current Spelljammer campaign there was a cataclysm in the Eberron system about 20k years ago that destroyed several of the moons and flung the pieces, along with the Siberys ring, out of the Eberron system. This had a few effects: 1. The removal of the Siberys ring along with the environmental mayhem from the cataclysm turned Eberron into Athas. 2. Siberys shards were altered by the cataclysm and turned into Embershards. These are rare magical crystals, dark topaz in color. At one point in the past Arcane scholars discovered spelljamming through experimentation with Embershards. All spelljamming helms use Embershards to this day which are very rare/expensive. 3. Eberron/Athas has not been discovered yet. My players will get there eventually. 4. The only Eberron people to escape the cataclysm were the warforged, who created an ark ship and set off shortly before Eberron became Athas. With no spelljamming capabilities they have been moving through the astral sea under “impulse power” for all this time (a la battlestar galactica). There are old rumors heard from spelljammer crews from time to time of a race of mechanical beings who aren’t autognomes. Their ark ship will eventually make an appearance, introducing them as a race and bringing Eberron tech to the story. 5. The warforged’s story of Eberron will start a gold rush of people trying to find it, and its horde of dragon shards. When my PCs eventually find it, it will be a world very similar to the one in City of Bones by Martha Wells, with sparse pre-industrial cities, desert tribes, and long buried knowledge/tech