Mad Moxxi’s Underdome Riot
The second piece of Borderlands DLC is now available. Mad Moxxi’s Underdome Riot introduces a new "riot" mode, in which you face "endless hordes of menacing antagonists, thirsting for carnage in tournaments where the rules of warfare are constantly changing." It seems that the add-on provides a series of tournament matches in the new "Underdome" arena, which is presided over by the titular Moxxi, a sarcastic lady. The battles will drop lots of high spec weapons, but not allow you to grind XP.
You can get the DLC for $10 at the Gearbox Store, or on Steam, but I can't say I'm that interested in this one. Trailer below.