 "Mass Effect 2" is set within the Milky Way galaxy during the 22nd century where interstellar travel is possible through the use of mass transit devices called Mass Relays, a technology believed to have been built by an extinct alien race known as the Protheans.A conglomerate body of governments known as the Citadel Council controls a large percentage of the galaxy and is responsible for maintaining law and order among races of the galactic community.Races that belong to the Citadel Council include humans, asari, salarians, and turians.