Time barrier
A time barrier was the barrier between alternate universes like Elysia and the prime universe.

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

See also
Temporal barrier
Temporal threshold

External link
 

de:Zeit-Barriere
fr:Barrière du temps
ja:タイム・バリア

 Time barrier