The Gauntlet

The Gauntlet is an area in the Challenge Node that Mario and Luigi can access in Mario & Luigi: Bowser's Inside Story. The Gauntlet is where the plumbers face X bosses, harder versions of bosses they have battled before. In the remake Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, Super Bowser's Giant Bosses can be refought here as well, where they are faster and more powerful, and no mushrooms will appear during the battles. The X bosses that can be fought in the Gauntlet are:

Mario Bros. Bosses
*Player must beat all previous classes in order to unlock.

Trivia

 * Scutlet, Chakron, the Dark Star Core, and the Shroobs are the only bosses that Mario and Luigi fight which don't appear in the Gauntlet.
 * If the Bros. lose against Durmite X before receiving the Badges from Princess Lipid, the Emoglobin at the door will still mention their existence.