The Brain

The Brain is a boss ghost that appeared in Luigi's Mansion 2, that can be encountered at the top of the ScareScraper.

Appearance
It is an unusually large Poltergeist that is fought on the roof of the tower. It has far more health than any other ghost and has a wide variety of abilities to fight the Luigis with. Unlike all the other bosses who are chosen randomly when a boss floor is reached, the Brain is always fought when the ScareScraper's roof is reached. The Brain has no texture variations and has always the same appearance.

Health
The Brain has a base health of 300 HP which increases by 200 HP for every player in the game with the official maximum being 900 HP.

The Brain's health increases in the following way:
 * 1 player: 300 HP
 * 2 players: 500 HP
 * 3 players: 700 HP
 * 4 players: 900 HP

Battle
Upon reaching the ScareScraper's roof, the player(s) must find and open the right chest that upon opening will trigger the boss battle. The Brain will appear alongside up to six support ghosts (which can be either Greenies or Slammers or any of their variants). The Brain will travel around the room invisible and throw several bricks at the Luigis. When it being vacuumed up, it will throw even more bricks towards the Luigis and after taking a random amount of damage it will push all the Luigis away with a giant shockwave. The Brain has a large pool of health and is always invisible, making it a hard boss to deal with.

Trivia

 * At 900 HP, the brain is the toughest ghost in the whole series, being nearly twice as tough as King Boo.