Hot on the heels of Borderlands first DLC, The Zombie Island of Dr. Ned, Gearbox revealed another upcoming DLC, Mad Moxxi’s Underdome.

The new content pack will have three Riot Arena’s filled with baddies (and loot!) and even feature a bank to store spare weapons. The DLC will also give two more skill points as rewards for quest and add new rules such as vampire mode or low gravity mode. Like the previous DLC, Mad Moxxi’s Underdome can be played in single-player mode and cooperatively online.

According to Gearbox’s Jon Hemingway, designer of the DLC on the arena quests:

“This is totally different [than the game]…basically the idea is that we have this character, Moxxi. She’s running this underground coliseum tournament arena thing. The best thing you could compare it to is either Horde mode in ‘Gears of War 2’ or Firefight mode in ‘ODST.’ But even those don’t quite sum it up.

“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.”

and on gameplay:

“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.  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.”

Borderlands players can expect the new addition post-Christmas on December 29th for Xbox 360 and PS3, with no announced date yet for PC. It will set you back 800 Microsoft Points ($10) or $9.99 on the PSN.