In the mirror universe, Locutus was the designation given to the assimilated Terran scientist Noonien Soong. Locutus was created on a Borg diamond in orbit of Carraya IV. Upon assimilation, he was augmented with a black ceramic implant on the left half of his face, equipped with a red laser sensor.

Under Locutus' leadership, the diamond devastated several colonies in Klingon space, including Beta Thoridar, Khitomer, and Morska, before heading for the Klingon homeworld Qo'noS itself. His diamond was attacked in the Kowletz system by a massive armada of ships from several races, including Klingon, Cardassian, Bajoran, and Ferengi.

Locutus died when his diamond was destroyed by an Iconian computer virus installed by Jean-Luc Picard. (TNG - Glass Empires novel: The Worst of Both Worlds)