The Borg transwarp portal was a large structure of Borg design. It's construction required the presence of a tachyon nebula. A stable, long-range transwarp conduit could be created between two transwarp portals. The Borg constructed one in the Bora system, in the Delta Quadrant, and linked it to another in the Suah'Dron system, located in the Regula Badlands of the Alpha Quadrant. Then, in 2377, they used it to send a large fleet of ships into the Alpha Quadrant. The invasion force was also accompanied by the Borg Queen.