Cantus was a human colony planet.
Irving Braxiatel travelled to Cantus with a Gallifreyan crystal and placed Ronan McGinley as the Cyber-Controller of Cantus, under his control. The Gallifreyan crystal became known as the Crystal of Cantus and gave a sense of mythology to the planet.
Years later, Braxiatel needed a new Cyber-Controller, and manipulated Jason Kane into going to Cantus with him. Braxiatel installed Kane as the new Cyber-Controller. After learning that this had happened to Kane, Bernice Summerfield took the Crystal of Cantus and used it to destroy all the Cybermen on the planet. (AUDIO: The Crystal of Cantus)