Misery Mansion is the common haunted house in the middle of a cemetery. Two upper windows are lit, creating the impression of giant glowing eyes from a distance. Once you pass through the grand double doors, there is no escape. If you jump out a window, you will drop into a black abyss filled with wailing Boos and Terekuribos.
Misery Mansion is ripe with vengeful spirits of all kinds. The easiest way to avoid them is to use Shadow Mario's Shadow Balls to turn them to your side. Portraits of Luigi appear on the walls, but leaping into them will not free Luigi. It will instead take you into an inescapable section of Subspace. Just past two Iron Goombas there is a black pit. It goes up as well as down, and King Boo is at the top. Bowser Jr. can use his Paint to make a ladder, or Waluigi can use his Cheating to air-swim to the top.
The King of Death is Exorcised
After King Boo's defeat, a closet door in the corner of the room will burst open. The Poltergust 3000 will be online, beeping to itself "Spectral activity at 100%". It will then power up and begin sucking Misery Mansion up as though it were one huge ghost. Within 5 minutes, you must escape the Mansion or you will be sucked up as well. After jumping out the window, either make a Paint bridge or air-swim over the void.