The Mad Moxxi's Underdome Riot Add-on for Borderlands has 5 trophies - 1 bronze, 3 silver and 1 gold.
Completed the larger challenge in The Angelic Ruins coliseum
Completed each of the larger challenges in all 3 coliseums
Completed the larger challenge in the Hell-Burbia coliseum
Completed the larger challenge in The Gully coliseum
Completed the lesser challenge in all 3 coliseums