The Battle Colosseum is the final stage of Mighty No. 9, and becomes accessible after clearing the Prison and the Robot Factory. Trinity is the boss of the stage. Just like the City and the Robot Factory, this stage is located in California.
Once Beck neutralized Nameless and M.O.M. and Call and Dr. Sanda talked to Dr. Blackwell, it became became clear to everyone that Trinity was the one behind both the virus and the robot uprising. After learning that she was using the Battle Colosseum as her base of operations, Beck had Aviator airlift him inside and fought his way through Xel-laden corridors full of shifting platforms and renegade robots to reach Trinity. She assumed two different forms to fight him - Trinity Cloud and Trinity Wurm - but was ultimately defeated, causing her body to explode and exposing a spherical core. Touching it allowed Beck to reconstruct Trinity's humanoid body, restoring her to normal and bringing the robot uprising to an end.
|Stage Theme (Retro Version)|
- The level music is a slower version of the Boss Battle theme.
- The Battle Colosseum is the only stage that features a vertical auto-scrolling segment.
- Standard enemies in this stage can be seen having cubes of Xels in them, showing that they were previously assimilated by Trinity and are now under her control.
- The fights with Trinity at the end of the stage take place one after the other, with no opportunity to rest or heal in between. If Beck loses a life while fighting Trinity's second form, he'll have to fight her first form again. Just like the battle against the Wily Machines in the Mega Man series.