Mad Moxxi's Underdome Riot is an addon pack for Borderlands that includes a new cooperative arena game mode and a stash to store your gear.
Are you god's gift to gun fights? Think you're the best? Wanna prove it? Then help us celebrate the grand opening of Marcus Bank (a subsidiary of Marcus Corp) by killing hundreds and hundreds of people in Mad Moxxi's Underdome Riot, the only competitive arena around where your next of kin can be assured that you're coming back famous . . . or not at all. (All proceeds are kept by us)

Multiplayer options may have changed, please see the main title for more information