Captain Boo Trial (Gold)
From the Super Mario Wiki
Captain Boo Trial (Gold) is the secret bonus level of Joke's End 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.
This is the seventh of seven bonus levels that involves a captain battling enemies by themselves. Captain Boo (Gold) is the selected captain to enter this level.
The level has two battles. The first battle has three Ice Snifits and an Elite Limbo Bro captain. The second and final battle has four Mechakoopas and a Piranha Bean captain.