Fearing their creators intended to exterminate them and with no alternative option, the Geth entered an alliance with the Reapers, allowing themselves to be controlled by the Reapers in exchange for gaining greater intelligence and fighting ability. The Reapers exert their control via a signal that is broadcast throughout the fleet. After Legion is rescued by Shepard and Tali inside a Geth Dreadnought, where it was trapped within a Reaper device in the warship's drive core, it decides to aid Shepard in the fight against the Reapers. They arrive at Rannoch, where the Reaper-controlled Geth are fighting against the Quarian army, who is trying to retake their homeworld. Legion sees no other option other than fight his fellow brethen for the future of the universe. During the invasion to the Reaper base in Rannoch, Legion and Tali find themselves separated from Shepard's main squad, and now must fend by themselves against the "heretic" Geth, but they will count with the help of one of the Geth Prime units that liberated itself from the control of the Old Machines.