Players assume the role of an elite human Spectre agent, Commander Shepard, entrusted with keeping law and order in the galaxy. The player uncovers a threat so great it could destroy all life in the galaxy. As the only human Spectre, Commander Shepard's job is complicated by the fact that no one will believe the word of a human, a race not fully trusted by the other alien races. However, the galaxy must be convinced of the grave threat at hand or all life could be exterminated.
Players will travel across an expansive universe to piece the mystery together. As they discover and explore the uncharted edges of the galaxy, they come closer to an overwhelming truth — learning that the placid and serene universe they know is about to come to a violent end and that they are the only being who can stop it. Throughout Shepard's exploits, players will face morally challenging decisions that will impact the future of all races, and how humans are ultimately viewed on the galactic stage.
Bob McKenzie, Senior Vice President of Merchandising at GameStop Corporation commented that, "Only a handful of video games redefine their genres, and judging from the excitement and demand we’ve seen from fans, Mass Effect for Xbox 360 is one that can bring role-playing games to a broader audience through its beautifully realistic graphics and cinematic, emotionally charged gameplay experience."