The Shattered Ring
The Prometheus Fragment is a segment of The Sundered Ring, and the only habitable location in the entire system.
For reasons unknown, the fragment has artificially generated gravity, together with a breathable atmosphere and functioning biosphere. No other fragment of the Sundered Ring has anything remotely like it, and the reasons for its uniqueness the subject of much theory – once built and fully functioning gravity should have been provided by centripetal forces caused by the Dyson Ring’s rotation.
One theory is that the Prometheus Fragment was home to the engineering crew that were in the process of building the Ring itself. They would have required a place to live, and so it is possible that the fragment was fitted with additional systems, such as artificial gravity generators, to give them that home.
If true the fate of those engineers is unknown – the Fragment had no indigenous population prior to its discovery, and no structures of any kind have been found on the surface to date.
(I intended to have the Sundered Ring be a series of habitable fragments with different function – e.g. the Prometheus Fragment being a wealthy sort of residential area, with others favouring commerce, lower-class neighbourhoods, manufacturing facilities and so on, hence the initial reference to the Prometheus Fragment being about rich inhabitants buying up large quantities of a fashionable accessory. Think the various different districts of the Citadel in Mass Effect. Can I suggest we revert to that plan, as it brings an awful lot more variety to the location? Sundered Ring can quite easily manage the technology to move between fragments – Alfie)
(Go for it! The above was just a stopgap. – Hedge)