Sphere 634 was a Borg sphere that was in service in the late 24th century. In 2378, Sphere 634 was one of the few ships the Borg Queen managed to maintain contact with after she'd been infected by Admiral Kathryn Janeway's neurolytic pathogen. The Queen sent Sphere 634 after the USS Voyager, while the ship was hurtling through the Borg transwarp network towards the Alpha Quadrant at amazing velocities. The sphere attacked Voyager, causing the ablative generator's armor integrity to drop to six percent, using the knowledge of the technology from the assimilated Admiral Janeway.