Mass Relay

Mass Relays are mass transit devices scattered throughout the Milky Way in the Mass Effect Universe. They form an enormous network allowing interstellar travel. A mass relay can transport starships instantaneously to another relay within the network, allowing for journeys that would otherwise take years or even centuries with only FTL drives.

FTL without time dilation is achieved using element zero that, when subjected to an electrical current, releases dark energy which can be manipulated into a mass effect field, raising or lowering the mass of all objects within that field. A positive current increases mass, a negative current decreases it. This "mass effect" is used in countless ways, from generating artificial gravity to manufacturing high-strength construction materials to FTL drives.

Like the Citadel, the Protheans were given credit for its creation but they were actually created by the Reapers.

See also: Mass Relay