- Eugenic Cult — Even in the days before the Silence, major improvement of the human genome always seemed to come with unacceptable side-effects. Some worlds host secret cults that perpetuate these improvements regardless of the cost, and a few planets have been taken over entirely by the cults.
- Flying Cities — Perhaps the world is a gas giant, or plagued with unendurable storms at lower levels of the atmosphere. For whatever reason, the cities of this world fly above the surface of the planet. Perhaps they remain stationary, or perhaps they move from point to point in search of resources.