Mad Moxxi's Underdome Riot

Mad Moxxi's Underdome Riot is the second downloadable content pack for Borderlands. The DLC was released for the Xbox 360 on 29 December 2009 and for the PS3 and PC on 7 January 2010.

Features

 * Three new Riot Arenas
 * Bank to store items
 * Two additional skill points as mission rewards
 * New game mode, with waves of enemies

Tagline
"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)"

Plot
Mad Moxxi is a thrill-seeking woman in search of a new husband. Having gone through three husbands already, her search has led her to becoming the Ring Master/Hostess and Commentator of the Underdome. She considers the Underdome and the excitement of the competition like matrimony and plans to stay only as long as the thrill lasts. Gameplay will include three new Riot Mode arenas where players will fight AI-controlled enemies (PvE) in single player or multiplayer. The expansion starts with a mission entitled "Prove Yourself" in which the player must complete all three arenas.

Mechanics
The gameplay consists of rounds and waves. Each round consists of five waves ending with a Boss wave. Every round brings an increased difficulty level. As the round number increases, the number of gameplay-altering Rules increases, adding variables such as different gravity levels and modified enemy regeneration, accuracy, damage, etc. If a character is incapacitated and fails to achieve a second wind in a multiplayer game, they will respawn in the Penalty Box on top of Moxxi's tower (from which they can still play an active role by sniping enemies) for the remainder of the wave. No experience is gained from kills inside the Underdome and consequently weapon proficiencies are not affected.

Rewards
You will be rewarded after the completion of each round, after you kill the boss, a few weapons of any quality a few levels below your own will spawn under the player spawn point. These weapons are usually of good quality, and you may have a fair chance of finding an Eridian weapon. Be sure to grab them before the timer runs out, and the next round begins.

Having more than one player in the arena fighting increases the quality, and amount of weapons after each round.

Achievements
The trophy list from a PS3 update revealed the following achievements associated with the new DLC.
 * Small Tournament Completed the lesser challenge in all 3 coliseums
 * Hell-Burbia Completed the larger challenge in the Hell-Burbia coliseum
 * The Angelic Ruins Completed the larger challenge in The Angelic Ruins coliseum
 * The Gully Completed the larger challenge in The Gully coliseum
 * Big Tournament Completed each of the larger challenges in all 3 coliseums

Trivia

 * The title "Mad Moxxi's Underdome Riot" is highly likely to be a reference to "Mad Max: Beyond Thunderdome".
 * As seen in the videos above in the wave video there will come different factions in this video you see etc. bruiser fighting a guardian making things more or less easier.
 * In the trailer for the DLC, when Moxxi's first husband is shown, the Konami Code (Wikipedia) runs across the screen, shooting him.
 * While playing in the tournaments you can occasionally hear the audience cheer "Heyo!" which is the famous saying of Steve the bandit who was supposedly one of her husbands. Steve is featured in many Borderlands promotional works, including the 'Borderlands Claptrap Web Series'


 * Moxxi's name is likely a reference to Roxie Hart from the broadway show Chicago which centers around the Roxie Hart and Velma Kelly, two acquitted murderesses who bask in the fame that being the "murder-of-the-week" brought them but showbusiness could not, an interesting relation to Moxxi's own love for violence due to lack of love otherwise and of course due to stardom, especially with some of Moxxi's commentary lines such as "Who loves you and who do you love!" (which is a quotation from "The Running Man," Schwarzenegger film where convicts fight to the death for the amusement of the masses) and, in the trailer, "and the audience will love me for my brutality". In the song "Cell Block Tango" the "merry murderesses" in the jailhouse describe the murders they committed, all on men, many for cheating, and features the memorable line "Pop, six, squish, uh-uh, Cicero, Lipschitz" referring to the reasons each woman killed the man (with the exception of "uh-uh" said by the Hungarian girl convicted because she could not speak English well enough to defend herself, when she did not, in fact, kill her husband). Moxxi would fit right in with the murderesses, having killed her first and seemingly led to the death of her second husband.
 * In the trailer Moxxi says "maybe I'll get my jollies off bringing pain this way..." which implies that her previous marriages caused primarily pain, which she enjoyed. This may imply her obvious nature as a seductress or a joke on marriage in general, saying that it is painful, often a joke made by complaining husbands and subsequently used by women to taunt them.

Glitches
This DLC has been known to cause glitches with some users. The cause has not yet been determined, but on occasion the DLC will delete equipped Shields, Class Mods and Grenade Mods. Instances of this have been linked to the "Naked" rule in the DLC. On many occasions this has happened when in multiplayer games with connection problems however it has also occurred in Single Player.

It has been suggested that players back up their save files prior to playing the DLC. On the PC, save files are located in the folder SaveData in Documents > My Games > Borderlands. On Xbox and PS3, an additional save should be made to an external device or external folder. If items have been lost, they can be replaced by overwriting the corrupted save file(s) with the backup. When replacing a corrupt file on a console the original file should be deleted first as many consoles do not allow overwriting.

Please keep in mind that backup save files must be kept up to date otherwise when they are utilized the user will lose all progress made since the last backup. To replace the save file of one character instead of all characters, the character's save file must be identified and only that file switched. Save files are numbered in order of chronology. For example, the first character created is named Save0001.sav. Save files are numbered Save0001-9 and Save000A-Z.

You should check your inventory after every session. If you find your shield/COM/grenades missing, try equipping a different one from your pack. Doing this may cause your missing items to reappear, albeit unequipped, in your inventory. This may not work if you have alread saved and quit while bugged.