Elysia is a small alternate universe, a parallel time continuum, that periodically touched the prime universe in the Delta Triangle region of the galaxy. Elysia was described by Devna, as a pocket in the garment of time. The collisions between the two alternate universes produced time warp vortexes in the time barrier between the universes. The warps allowed passage from one side to the other at high warp speed.

Elysia was governed by the Elysian Council. Its "starship graveyard" contained all of the ships lost in the Delta Triangle over the millennium preceding the arrival of the USS Enterprise. While time passed at the same rate, the effects of time, like aging, occurred at an extremely slow rate in Elysia relative to the outside universe. All acts of violence were forbidden in Elysia, and were stopped by the members of species with psionic powers. According to some of its inhabitants, "Elysia is, in many respects, a perfect society. But with all its virtues, it is not home. And home, with all its faults, is where we prefer to be." (TAS: "The Time Trap")