The Mass Effect world is filled with fascinating aliens that stretch the bounds of imagination. One of the most interesting of these groups are the geth, an AI race created by an organic species, the quarians, who rebelled against their creators. The geth are introduced as an antagonistic group in Mass Effect, then make a surprising face-turn in Mass Effect 2 with Legion, who joins Shepard's team. By Mass Effect 3, they're understood as their own independent, intelligent form of life.