Elysia is a Class M planet located in a sector of the galaxy that is not opened by the Federation for general transit, due to the lack of starship support facilities. The planet appears to have been terraformed, as in its present configuration, it could not have developed naturally. Nearly the entire planet is a swamp with a noxious atmosphere, but there are ten anomalous areas, each with a breathable atmosphere, with a force field of unknown form keeping the swamp atmosphere from overwhelming the small habitats.