Elysia

Elysia was the name given an interdimensional region within the Delta Triangle area near the Federation-Klingon border, as well as the name of the society that had formed there.

For centuries, starships from cultures across the Alpha and Beta Quadrants had mysteriously disappeared in or near the Delta Triangle. In 2269 the USS Enterprise discovered a "pocket universe" into which these vessels, and their crews had disappeared, and become trapped by the unique energy and temporal qualities of the region. Time within Elysia passed much more slowly than in the outside universe, allowing ship survivors extended life spans.

The survivors of those crews joined together for mutual survival and cooperation, eventually creating the society of Elysia, ruled by a body called the Elysian Council. Despite the multitude of different beings that made up Elysia, it was in many regards a near-perfect society. (TAS episode: "The Time Trap")

Later in 2269, the crews of the USS Lovell and the USS T'Saura determined a way for those trapped in Elysia to return to the outside universe. This development convinced a number of residents to leave Elysia and return home. However, following a conflict with several Gorn vessels seeking to extradite a Gorn criminal from Elysia, the Council negotiated an agreement with Federation Ambassador Robert Fox to have Elysia declared off-limits to the rest of the universe.

Over a century later, in 2376, the USS da Vinci, at the request of the leadership of planet Valzhan, transported Guardian Royano to Elysia, to present the jelorakem of Clan Briphachi to Saraven, a member of the Elysian Council and the last surviving member of that extinct clan. (SCE eBook: Where Time Stands Still)