Mass Effect Team Assault was a planned first-person shooter game set in the Mass Effect universe that later formed the basis for Mass Effect 3's cooperative multiplayer mode.
Team Assault was intended to be a downloadable competitive multiplayer game. It was developed for four months in 2010 following the release of Mass Effect 2 before the idea was set aside and used to create the multiplayer mode in Mass Effect 3. The existence of Team Assault was revealed through a behind-the-scenes documentary of Mass Effect 3's development, "The Final Hours of Mass Effect 3".[1]