Mad Moxxi is the host/MC of the colosseum-style matches of The Underdome featured in the second DLC for Borderlands, Mad Moxxi's Underdome Riot. Little is known about Moxxi other than that she has been married at least three times. Her first husband has yet to be revealed (although she may have also been married to Lucky Zaford), her second husband was Mr. Shank (a.k.a. David), and her third husband was Marcus Kincaid. She is an unapologetic sadist, and created The Underdome to keep herself occupied until she finds herself a new husband.
She is also part of the main storyline in The Secret Armory of General Knoxx (the third Borderlands DLC), where she sends the vault hunters to deal with her second husband and rescue Athena, and runs the bar Moxxi's Red Light. Scooter also reveals in The Secret Armory of General Knoxx that Moxxi is his mother, meaning that she has at least two children, Scooter and Scooter (the unseen sister Scooter was named after).
Moxxi is voiced by anime favorite Brina Palencia.
Mad Moxxi appeared in the non-canon trailer for the Game of the Year edition of Borderlands. Claptrap at one point complains that the trailer is very expensive to make, citing having "so many celebrities in once place" as the cause and claims that Mad Moxxi alone contributes greatly to this, drinking "diamond-flavored water". Shortly after this Moxxi questions Claptrap's decision for her to wear a Skag-skin bikini during a scene where she is in an Arctic ruins, to which Claptrap retorts "nipples are part of the plot", Dr. Zed also mocks Moxxi. Moxxi also appeared in the trailer for Mad Moxxi's Underdome Riot, telling the story of her previous three husbands and briefly appearing in The Underdome.
It would seem that Mad Moxxi's place in the Borderlands universe is directly inspired by the cult Australian film series Mad Max, specifically the third entry, Mad Max Beyond Thunderdome. The notion and name of the Thunderdome and Underdome are practically the same, with Moxxi acting as Borderlands' equivalent of Aunty Entity, portrayed by Tina Turner in the film. Mad Moxxi's name also appears to have been derived from that of the Mad Max saga's eponymous protagonist, the second such reference to the cult classic.
Sample Moxxi Quotes from Mad Moxxi's Underdome Riot
- "You get your kicks by killing things? That just sick, just sick! You know, I'm kind of sick myself."
- "It's raining body parts! Who do you love?"
- "Did I promise you a show, or didn't I? Who loves you, and who do you love?"
- "Ha! Look at that, I think you tickled it."
- "I think I just spilled something on my dress, damn it! Oh yeah and nice wave, whatever, damn stain."
- "Eeeeee! Gooooo! GOOOOOO! KILLING SPREE!!"
- "And pop goes the weasel. I love it when things pop!"
- "Another head goes boom!"
- "Look at that little Lilith, Mmm Mmm Mmmmm."
- "Your baby blues may work on me, but will they work on THIS?"
- "Pew pew pew! It's gun wave time!"
- "You may think you're shit hot, but you haven't seen the BADASS wave yet!"
- "The Horde Wave is comin' to eatcha! OM NOM NOM NOM!
- "Here come the BADASSES!"
- "Don't let this flood of flesh overcome you, the HORDE WAVE!"
- "Life is a circle... feelin' like a hamster?"
- "Ouch. I think that'll leave a mark."
Sample Moxxi Quotes from The Secret Armory of General Knoxx
- "What can I do you for? Wait... I'm not that kind of girl... Wait... Yes I am..."
- "You need somethin' sweetie?"
- "Nice of you to drop in on lil' ol' me."
- "Well hello there."
- "You look like you could use a drink."
- "You need me again, sweet lips?"
- "If you need any of my services, you know where to find me."
- "Now he's turned it into his personal male stabbing machine. He he, that's what she said! High-Five!... Nobody?