Mack is one of the Smithy Gang, and one of Smithy's lieutenants. He has the appearance of a dagger, and commands an army of Shysters. He also knows powerful fire magic, but is one of Smithy's weakest followers.
While Mario and Mallow were chasing down Croco, Mack and the Shysters took over Mushroom Kingdom. Once a high enough level from defeating many of the unlimited Shysters, Mario and Mallow entered Peach's Castle and fought Mack, with four Bodyguards. All of them were defeated, including Mack. Mario took the first Star Piece after his victory, while the two remaining Shysters left to inform Smithy of Mack's demise.
Mack has 480 HP, 22 ATK, 25 DEF, 15 magic attack, and 20 magic defense. He fights alongside four Bodyguards. He uses the magic attacks Flame Wall and Flame. At one point, Mack will jump up out of the battle, and not re-enter until the bodyguards were destroyed.
His Psychopath thought is "Boing, boing, boing. Mario! I'm BAAAAAAACK!"