You’ve been teased and told what to expect but BioWare has put up a Special Edition of BioWare Pulse to tell all of us gamers face to face about Mass Effect 3’s Multiplayer, check it out! And if you still have lingering questions BioWare has a small FAQ here answering specific question most gamers will have. The most common one we will put here “why is it co-op only multiplayer?” Because “Fighting together against a common threat was the multiplayer experience that made the most sense for Mass Effect 3.”
Source Link: YouTube | Mass Effect BioWare Multiplayer Link
