[Astromancer]

Which all sounds like the various barbarian successor states to Rome.

Unlike the Roman analogy some worlds would be low population because of recent settlement. Given the Vilani were unprepared for Terran diseases, some worlds might have plunged down to the low millions. Terran setters might try to help, but until the Vilani develop resistance to Terran diseases, their populations can't grow. Some Long Night worlds would therefore be struggling frontiers.