In Mass Effect - BioWare's sci-fi role-playing game for the Xbox 360 and PC - the galaxy is trapped in an endless cycle of extinction. Every 50,000 years, an ancient machine race invades the galaxy. With ruthless efficiency, the machines wipe out all advanced organic civilization. They leave behind only the scattered ruins of technology, destroying all evidence of their own existence. Few believe this ancient legend. You, however, know it to be true. The fight to stop this extinction event has become the most important mission in the galaxy.