Vesperia, sometimes referred to as Vespiria, is a natural satellite and Vesper's third moon, and the birthplace of Ryuusei Cartwright.
Little is known about Vesperia, except that it was inhabited by the Vesperian race, whose existence came into being in there rather than in Vesper itself, due to the planet's inhospitable conditions.
No records of what happened to it, nor even that it ever existed, can be found. This suggests Vesperia's civilization evolved much culturally and technologically, but eventually fell into corruption and was likely uncreated by The'Galin, according to Falerin Ardendor[1]. Some inhabitants were spared though, having become part of the Network, and were scattered across other worlds.
Two such are Elizabeth Twain and her son, Ryuusei, who were cast out to Terra[1].