Borderlands: Mad Moxxi's Underdome Riot serves as an arena-focused addon for the original Borderlands action RPG on PC. It adds cooperative wave-based combat in dedicated coliseums along with expanded storage options for gear. Players enter a central hub to access three distinct arenas and test their builds against escalating enemy waves in a format that emphasizes survival and team coordination over open-world exploration.
Gameplay
The core loop revolves around entering arenas through the Underdome hub and surviving structured rounds of combat. Each round consists of five waves that conclude with a boss encounter, with difficulty scaling through added modifiers such as altered gravity, boosted enemy accuracy, or increased damage output. Enemies arrive in groups that grow more aggressive over successive rounds, requiring precise positioning and weapon management to clear objectives.
Characters do not gain experience points from arena kills, which shifts focus toward testing equipment and completing separate challenges for progression rewards. In team play, incapacitated players enter a penalty area where they can still contribute by firing from an elevated position until the wave ends or the group resets. Loot drops occur at the end of rounds from the host, scaled to the current level, while a dedicated bank allows storage of items between sessions.
Single-player runs follow the same wave structure but lack the penalty-box support, making coordination and self-revives more critical. The system rewards consistent performance across multiple rounds rather than one-off engagements.
Game Modes
The primary addition is Riot Mode, a wave-survival format hosted in three specific arenas: Hell-Burbia, The Angelic Ruins, and The Gully. Initial access requires completing the Prove Yourself mission, which involves finishing five-wave runs in each location. Once unlocked, players gain unlimited replays of the arenas with expanded challenges that extend the number of rounds and intensify the modifiers.
These modes operate in both solo and cooperative settings, with enemy spawns and boss waves designed for group scaling. No other modes or story-driven campaigns appear in the addon, keeping the experience centered on repeated arena clears and achievement hunting tied to completion of lesser and greater challenges in each coliseum.
Arena Design and Progression
Each of the three arenas presents unique layouts that influence movement and engagement tactics during waves. Modifiers applied per round force adaptation, such as changes to enemy regeneration rates or accuracy, which compound as rounds advance. Completion of the base challenges opens larger tournaments that demand sustained performance across extended sessions.
Progression ties directly to these arena clears, with skill point rewards available upon finishing the initial mission in each playthrough. The bank feature integrates with existing inventory systems to manage gear without interrupting arena flow.
Is It Worth Playing?
This addon appeals most to players who enjoy focused co-op arena combat and repeated wave-clearing sessions within the Borderlands universe. It provides a compact alternative to the main game's exploration, with mechanics that highlight build testing and team revival strategies. Reception has been mixed, with praise for the challenge scaling in groups but criticism for repetition and limited variety when played solo.
The content remains available as a standalone purchase on PC without ongoing seasons or updates. Those seeking short, intense co-op encounters may find value in the arena format, while players preferring narrative depth or open progression might skip it in favor of the base game or later entries. Availability depends on ownership of the original Borderlands title.
