This new DLC pack allows you to play as Wallace Wells, Scott Pilgrim's roomate. Of course, it also allows you to play online with other players. It'll cost 160 Microsoft Points for the privilege and the extra character.
While this story may seem cut and dry, Scott Pilgrim creator Bryan Lee O'Malley stated late last year that he was never contacted in regards to producing this DLC. Whether or not Ubisoft just went ahead without the normal development squad is yet to be known, and the DLC has been delayed at least once. We'll find out all of the details soon.