Big Boo Battle

Big Boo Battle is the second boss level of Super Mario 64 DS. Upon completing it, Mario will earn the key to unlock Luigi.

This level is actually a pocket level of Big Boo's Haunt, which is where the entrance is located. However, this level is confusingly named; The boss that Mario fights appears to be King Boo, not Big Boo.

Being a pocket level of Big Boo's Haunt gives Big Boo Battle a haunted house setting. It is a maze, and the goal is to find the correct path, as the wrong path (or simply falling) will warp Mario back to the start, similar to what can happen in Forever Forest in Paper Mario. To find the correct path, the player must listen to King Boo's laughter in the background, and sense which direction they should travel in.

There are two Power Stars in this level; One for finding eight Red Coins, and a hidden one. However, they cannot be obtained on the first trip through the level, as Wario is needed to break a black Brick Block containing a Red Coin, while the hidden Star is behind a Boo portrait in the last room and requires Luigi's Power Flower ability to reach.

The entrance to the level is the Luigi painting on the third floor of Big Boo's Haunt, that requires Mario's Power Flower ability or Luigi or Wario's backflips.