Byrus is a planet packed with rare metals and the home planet of Rush. It was violently conquered by the Crogs, who destroyed it and took all its resources. One of those resources was sorgonic metal, an invaluable and indestructible substance. Apparently the Crogs didn't get all of it, however, as Rush's star-racer, the Stone Crusher, is made of sorgonic metal. Also, the Crogs severely polluted the planet in search for the sorgonic metal.