A Muster of Masks
From the Super Mario Wiki
A Muster of Masks is the second secret level of Teehee Valley in the Minion Quest: The Search for Bowser mode in Mario & Luigi: Superstar Saga + Bowser's Minions. In order to obtain this level, the player has to use certain amiibo to unlock it.
The levels contains mostly Shy Guys, Fly Guys, and Bandits and has three battles. The first battle has four Fly Guys at the front, three Shy Guys at the back, and a Bandit captain. The second battle has four Fly Guys at the front, three Bandits at the back, and a Shy Guy captain. The third and final battle has two Fly Guys at the front, two Bandits and two Shy Guys at the back, and a Fly Guy captain.