Temporal Vortex
A Temporal Vortex is an artificial phenomenon which allows a device, individual or vessel to travel through time and space. At present only two species are known to be able to create such a vortex.
These are the Borg and the Tkon. In 2397, the Borg uses just a vortex in an attempt to prevent first contact and thus the founding of the United Federation of Planets. The Borg are known to have only two ships capable of producing such a vortex, a Borg Sphere and a Borg Pyramid.
Later in 2414, another such Vortex was created by a Borg Pyramid in an attempt to travel back through time to the decline of the Tkon Empire. The Vortex was successful although the Federation starships, the USS Rosenante and the USS Boudicca also made the journey. In this instance the Borg vessel did not travel far spatially, beginning and ending it's journey at Dovek II.
Just a few days later, the Borg captured a device known as a Tkon Nanosphere and used it to travel backwards through time and space to Earth. Once again the two starships followed and prevented the destruction of mankind.
Both vessels were sent back to their respective times when a Temporal Wave overcame them after the destruction of the Tkon Nanosphere
