Mass Effect 3 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 based out of the Citadel, an ancient space station, 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, the blue-skinned asari, the lizard-like salarians, and the avian turians. Other alien races seen in the game include the reptilian krogan, the environmental suited quarians, the four-eyed batarians, and a race of networked artificial intelligences called geth. During the events of the original Mass Effect, the Reapers, a highly advanced machine race of synthetic-organic starships that are believed to eradicate all organic civilization every 50,000 years, attempted to launch a full-scale invasion of the Milky Way, but were delayed by the efforts of the Systems Alliance, humanity's representative body in the interstellar community. Meanwhile, a human supremacist organization called Cerberus believes that humans deserve a greater role in the galactic community and supports the principle that any methods of advancing humanity's ascension are entirely justified, including illegal experimentation and terrorist activities.