The homebrew setting I'm running and developing in my Dungeons & Dragons 5e campaign consists of an endless universe filled with infinite worlds. Since I can't create infinite worlds on demand, I've divided the universe into star sectors, each containing a number of worlds. These worlds, not planets, are any celestial bodies inhabited by humanoids, acting as different planes accessible through chappa'ais (magical portals from an ancient civilization), magic, or spelljammers. Currently, the PCs are in their home sector and can travel between about 10 different worlds (so far, at level 12, they've visited a total of 5).
Separate from these worlds but withing the same sector, is Astra Taldea, a group of asteroids bound and connected to each other by ancient and gargantuan magical chains, forming a kind of archipelago. This group of asteroids travels through space along this star sector, pulled by a herd of colossal and ancient kindoris.
Astra Taldea is formed by asteroids similar to Rock of Bral and is inhabited by five humanoid races: the Astral Elves, the Githyanki, the Tenno humans, the Skittermanders, and the Plasmoids. These humanoids possess technology similar to Treasure Planet and Spelljammer. The Astra Taldeans rarely travel to the other worlds in the sector, and some are unaware of their existence.
No one truly knows who formed Astra Taldea, but it wasn't any of the races that inhabit it today, despite each race's legends claiming it was them.
Astra Taldea won't be accessible during this first campaign, but it will be during the next one. I would like some ideas to elaborate futher more Astra Taldea for this second campaign.
EDIT: I'm looking for location, point of interest or hook ideas.