Bora

The Bora system was a star system located in the Delta Quadrant. It was controlled by the Borg Collective, which had a large presence in the system. It also contained a large amount of radioactive nebulae- including a transphasic nebula. Federation warp drives did not function in this system, which might have been due to the radiation from the nebulae or due to some other anomaly.

In 2377, the Borg chose to construct a transwarp portal in this system, and link it to another portal in the Suah'Dron system of the Regula Badlands (in the Alpha Quadrant). They then sent a large fleet of ships through the portal to assimilate the Alpha Quadrant.

The Federation, however, counter-attacked, seizing first the portal in the Alpha Quadrant, and then the portal in the Bora system. The Bora system was fortified by Starfleet, but it was later attacked by both the Borg and Species 8472 when the Federation expedition force attempted a withdraw. Because the portal in the Alpha Quadrant was destroyed, a small group of Starfleet ships, including the USS Enterprise-E was stranded in the Bora system.