The playable characters in the multiplayer component of the game will not be included in the campaign, so they will not be effecting the story whatsoever. “They will never be involved in the actual campaign of the main story,” producer Jess Houston said in an interview on the BioWare blog.
“It’s more like a side mission to the single-player. We don’t want to create situations where multiplayer players have something that single-player players couldn’t otherwise see.”
“At a high level, Shepard is marshalling the troops on behalf of the Earth Alliance so you are technically fighting for the Earth Alliance,” Houston continued, talking about the multiplayer now. “From a story perspective, a lot of these groups have come together as a loose fighting force to stop the reapers therefore they don’t fly the same type of banners that would have existed in pre- reaper invasion days.”
Mass Effect 3 releases on PC, Xbox 360 and PS3 on March 6 next year. Stay tuned for more info.