In Mass Effect 3, an ancient alien race called the Reapers launches a massive invasion across the galaxy, leaving nothing but destruction and misery in their wake. The invaders succeed in conquering Earth, and life in the galaxy is on the verge of extinction. The only chance for salvation lies with the players, who, as Commander Shepard, must lead a counterattack to reclaim the Blue Planet. If they fail, the fate of the entire civilization is sealed. Only the players can determine the outcome of individual events, which planets will be saved from extinction, and which alliances they will form or abandon in an effort to gather the forces of the galaxy to eliminate the Reaper threat once and for all.