Secret Altar

The Secret Altar (Japanese: 秘密の祭壇 Secret Altar) is the final room in Luigi's Mansion. It is found in Area Four and is where the game's final boss, King Boo, awaits.

The Secret Altar contains three chandeliers, one of which holds a Blue Stone. On the west wall is a stone lion's head on the other side of which is the Bottom of the Well (which is where the player first encounters the room). On the east wall is a mirror flanked by two torches burning with incense. If Luigi vacuums the incense, one torch will give him money, and one torch will give him a gold bar. Two similar torches are found at the rear of the room on either side of Mario's painting. These and the two chandeliers near King Boo can be vacuumed, but they do not yield anything.

After Luigi retrieved the spade key in The Artist's Studio, it allowed him to gain entry past the forcefield guarding the Secret Altar. Stepping inside the shiny, golden room, Luigi found King Boo, staring forlornly at a painting of Mario. This was no mere painting, however, as the red-clad plumber himself was trapped inside. As Luigi approached, King Boo launched into a long speech about the two brothers. How Mario caused him so much trouble in the past, and how Luigi vacuumed up all his friends and minions into his vacuum. King Boo tells Luigi that he is not afraid of the ghost hunter, only the Poltergust 3000 he carries on his back. His final threat is for Luigi to join his brother inside the painting. King Boo transforms Mario's painting into a painting of Bowser, which he flies into. The Bowser painting inhales Luigi and the green-garbed ghostbuster finds himself on the roof of the Mansion, staring down King Boo inside the reanimated body of Bowser. King Boo attacked Luigi, but Luigi was able to defeat him after isolating him from Bowser's body.

After Luigi completely depleted King Boo of energy and the leader of the Boos was sucked into Luigi's trusty vacuum cleaner, his crown became Luigi's, and the Bowser body fell in two pieces, unable to move without King Boo's guidance. Luigi was warped back to the Secret Altar, where he finally recovered Mario's painting to return his brother to his former self.