Kotaku reports in an updated post via word from Randy Pitchford:

Gearbox Software says that Mad Moxxi’s Underdome Riot is “not just new deathmatch areas.” CEO Randy Pitchford notes “This is an ENTIRELY NEW GAME MODE.”

“Think [Halo 3] ODST’s ‘Firefight’ or Gears of War’s ‘Horde Mode.’ Cash, prizes and competition!” Pitchford said in a statement from Gearbox. “It’s like Smash TV in coop FPS, but in the Borderlands.”

Gearbox reps say the new Borderlands downloadable content “expands greatly on the possibilities of combat as well adding a ton of new rules such as vampire mode or low gravity mode…”

MTV MP Blogs reports that the harder arenas might take six hours to complete:

It’s all about this crazy Moxxi character, and she’s running these tournaments. You go in and fight waves and rounds of monsters, and then she starts changing it all up. She throws out what are called ‘Moxxi Maxims,’ these rules that dramatically change the way the game play. She’ll be like, ‘Vampire Rule!’ which makes it so that the player’s health is constantly draining, but every time you get a kill you get a whole bunch of health back. Now all the players are like, ‘Holy crap, I have to play amazingly aggressive,’ so you have to charge in before you basically bleed out. Another example, she’ll go ‘Shotgun Challenge,’ where all shotguns do bonus damage and all other guns take a penalty.”

There’s a small tournament and a big tournament. The small tournament takes probably about an hour, and most people will be able to get through that. The big tournament…one of the things people have been asking for is for something that challenges them, and that’s what the big tournament is. I think the last time I went through it, it took me six hours to get through a big tournament. You can’t save your progress, you have to do it in one sitting, but you can stop, walk away from it and come back [Ed note: You just can't turn the system off]. It’s really hardcore. To get through the big tournament, you’ll have to get some friends who are very good and you’ll all have to plan out what people are going to do and what weapons you’re bringing.”

There are also three screenshots total now, see them all below (click for larger versions)

Great Job Dennis.  Would you kindly make an 87bazillion.com one?

via Kotaku