The second expansion for Gearbox Software's Borderlands is now accepting contestants and Microsoft Points. Mad Moxxi's Underdome Riot is now available for the Xbox 360 version of the game, giving Borderlands loot hounds new areas in which to grind.

What does one get for the 800 Microsoft Points investment? The all-new Riot Mode challenges, offering new things to loot and a bank in which to store all that loot. It may not sound like much for ten bucks, but the description "like Smash TV in coop FPS" seems to actually have some truth to it, making the DLC potentially priceless.

You can read our impressions of the new downloadable content if you're on the fence or, if exceptionally cautious, wait for our upcoming review.

Mad Moxxi's Underdome Riot hits the PlayStation Network beginning January 7, 2010 for $9.99 USD and Windows PC in "early 2010." Anyone grab it yet?