This level is consequently the final level in NSMB Steam, located in World 9-9. It is analogous to most final challenges, and is designed to be the hardest level in the game, similar to The Final Final Test Badge Marathon. This level uses the last phase final boss theme from NSMBU, however no boss battles are present. To compensate for this, a very hard obstacle course replaces the boss battle as it is designed to be the hardest level in the game.
9-9: The true final stage of NSMB Steam. It is designed to be the hardest level in the game with the final boss theme from NSMBU being played over the level. It has no checkpoints, as a way to increase the level's difficulty and challenge.