Mass Effect 3 is the story of the grand galactic war, a World War II metaphor where the ultimate evil has arrived, threatens to dominate and destroy everything, and only a grand alliance of every not-evil group in the galaxy can defeat them.
There are two overall themes in Mass Effect 3: war and resolution. More than its two predecessors, Mass Effect 3 utilizes its level design, combat mechanics, and more in order to harmonize its gameplay with its story.
But the story of Mass Effect 3 isn't isolated from the rest of the game. Oh, don't get me wrong-the story is incredibly important to the game, and it's mostly great, albeit with, ahem, a few teensy-weensy issues at the end. Here's the thing, Mass Effect 3 isn't a great game because of its story. That's understandable, but it sells Mass Effect 3 short. And with the sheer amount of emotional investment players had over multiple games and years, the first thing everyone talked about with Mass Effect 3 was its story. That's usually a recipe for at least mild disappointment. Not only was it a sequel to one of the most acclaimed games of all time, but it was also the end of an epic science fiction trilogy. The final game of the Mass Effect trilogy was always going to have a difficult time.
