Challenge Node

Challenge Node is a location inside Bowser's body that appears in the game . The Challenge Node is a special place where Mario and Luigi must pay coins in order to to fight stronger versions of previous, faught bosses for prizes. Mario and Luigi can also use their Special Attacks in this area as a challenge. The Challenge Node is located directly beside Toad Square and directly above the Flab Zone. The Challenge Node is the only area inside Bowser that does not need to be visited at any point in order to complete the game.

The Gaunlet
This is the mode where Mario and Luigi must pay coins in order to fight previous bosses. However, these bosses are much stronger than the regular ones and some even are required to beat in a given amount of turns.

Bosses

 * Durmite X: A stronger version of Durmite. Mario and Luigi must pay 200 coins in order to fight it. They must also beat this boss in five turns or less. The reward is 1000 coins.
 * Alpha Kertin X: A stronger version of Alpha Kertin. Mario and Luigi must pay 400 coins in order to fight it. They must also beat this boss in 15 turns or less. The reward is 2000 coins.
 * Wisdrum X: A stronger version of Wisdrum. Mario and Luigi must pay 800 coins in order to fight it. They must also beat this boss in 18 turns or less. The reward is 4000 coins.
 * Bowser Memory ML X: Stronger versions of Bowser Memory M and Bowser Memory L. Mario and Luigi must pay 1,200 coins in order to fight them. They must also beat the bosses in 10 turns or less. The reward is 6,000 coins.
 * Junker X: A stronger version of Junker. Mario and Luigi must pay 1,800 coins in order to fight this boss. They must also be this boss in 15 turns or less. The reward is 9,000 coins.
 * Dark Star X: A stronger version of Dark Star. Mario and Luigi must pay 2,500 coins in order to fight this boss. They must also beat this boss in 12 turns or less. The reward is 12,500 coins.
 * All X Bosses and Bowser X: Mario and Luigi must fight all of the previous bosses again before fighting Bowser X: a stronger version of Bowser. Mario and Luigi must pay 5,000 coins and beat all of these bosses in 35 turns or less. The reward is 25,000 coins.