A Klein sphere is an extreme astronomical effect that could be used, under certain conditions, to completely isolate a large section of space within a barrier impenetrable to any matter, such as a starship.

On stardate 4107.6, in the 2260s decade, the United Federation of Planets erected a Klein sphere around over 1,000 star systems somewhere in the galaxy's Alpha or Beta Quadrants. This so-called quarantine zone was to try to control a telepathic outbreak of mutiny caused by a rogue Klingon admiral. If the starship USS Enterprise had been unable to stop the mutiny outbreak, Starfleet intended to adjust the Klein sphere to be permanent. (ST video game: The Rebel Universe)

While the mechanics of the Klein sphere were simply intended to provide a dramatic foil for the gameplay of The Rebel Universe, there are questions raised as to why Starfleet or the Federation would fail to use this effect in other dire situations. Possibly, the situation centered at Dakiak had unique properties that made this effect possible and they would be unable to duplicate the effect in other parts of space.
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