I've been reading through the Starfinder source book, Pact Worlds. It's a small book, but fits a lot of information into it, so I'm going to post about sections as I finish them.
The Diaspora is an asteroid field between the planets Verces (and the generation ship Idari) and Eox. It's existed for a long time, but it wasn't always an asteroid field. From the Paizo Pathfinder publication Distant Worlds:
Azlanti scholars reference two more worlds: the Twins, Damiar and Iovo, orbiting at a point between Verces and Eox. Damiar and Iovo were close enough that the planets spun around each other in the course of their orbits, and their residents were likely the first sentient races in the system to achieve interplanetary communication and trade.
Pathfinder's playable timeline started well after the Lost Ones got supplanted by an asteroid field. Because this is Starfinder and I've become annoyed by The Gap, I may as well mention now that nobody remembers, even in Distant Worlds, what happened, and that's fine. No mysticism is required, there's no bright neon sign announcing a gap in the timeline. We're just told that history is unclear about what happened, and it seems perfectly natural. I quite appreciate that (although to be fair, it's less of a significant event in the sense that no Pathfinder adventure expects or cares whether the GM understands differences in architecture and technology of pre-Diaspora and post-Diaspora.)
Like in any good sci fi universe multiverse, this asteroid field isn't just an asteroid field.
It's well populated by NPCs and monsters alike.
The major NPC faction are the Free Captains, a group of space pirates that take advantage of the Diaspora for the free-for-all frontier that it is.
They maintain a base there, called Broken Rock, and it's presumably the Mos Eisley or Tortuga or Port Royal of space piracy.
There's also a smattering of several other factions.
The Diaspora is fertile ground to plant whatever you need, whether it's pirates, scientists, cults, monsters, treasure hunts, abandoned ships, shipwrecks, and so on.
There's no shortage of story seeds in this section.
There's an old Corpse Fleet outpost called Cairn. The book makes it seem like there's a big signpost out front advertising that it's an abandoned and possibly haunted munitions dump, but that everything of value was looted long ago. Personally, if I take my players to the Cairn, they're definitely going to find cool loot (but not after navigating their way through a few deadly traps).
There's a timeloop trap on EC-40, a comet that was a little too close do Damiar at the moment of the planet's destruction (or transcendence, or whatever happened.)
An old ysoki ship, the Farabarrium, now serves as a trade center.
The Forgotten King is an asteroid that looks like a 12-mile in diameter human skull. The interiour of the asteroid is inscribed with thousands of lines of poetry that have, so far, defied even magical translation.
There's an asteroid called Parley, which emanates a magical field that prevents anyone nearby from telling a lie.
The list goes on and on.
I've decided that the Starfinder worlds need shorthand descriptions, the way one might refer to Magic: The Gathering planes by theme. Innistrad is gothic horror world, Zendikar is Tomb Raider world, Amonkhet is ancient Egypt world, and so on.
The Diaspora admittedly defies this model, because it's not a single unified place. But that's its strength. It's a little like 5e's Domains of Dread without the mist. It's a region of easily accessible space that can have whatever mini-setting you need.
Broken Rock could be a great homebase for rogue-ish players, too. I'm willing to bet that a quick read-through of Frog God Game's Freebooter's Guide to Razor Coast and 5e's Ghosts of Saltmarsh could provide plenty of pirate-based adventure ideas that would be easy to translate into space adventures.
Header photo by Seth Kenlon, Creative Commons cc0.