Tkon Nanosphere
The Tkon Nanosphere was a probe-like device built by the ailing Tkon Empire 60,000 years ago. Built on Dovek II, the device was intended to be used to seed specialized nanites into the atmosphere of that planet.
Those nanites would then begin the process of breaking down high-energy radiaoactive particles that were bombarding the planet from the remnants of the Supernova that destroyed the Tkon Empire.
In 2414, the Borg sent an expedition to Dovek II led by a drone named Volus. His mission was to locate and recover the ancient device with the hopes of using it to seed Born Nanoprobes into a planet's atmosphere, thus accelerating the process of Assimilation.
Volus was a firm believer in Borg Philosophy and as such was granted a great deal of individuality by the Borg Queen.
The Tkon Nanosphere was first seen in the joint USS Boudicca and USS Rosenante mission Once More Into The Breach
