Treacherous Mansion

The Treacherous Mansion is the final and longest mansion that Luigi visits in Luigi's Mansion: Dark Moon. It has a museum theme and it is also the location of the final Dark Moon piece, as well as being the location of the highest paranormal signals ever recorded. Many rooms on the first floor of Treacherous Mansion are based off of the previous mansions in the game. Also, almost every ghost that Luigi encounters appear here. King Boo comes to this mansion to open a Paranormal Portal to unleash almost every ghost that Luigi has ever encountered, such as Greenies, Slammers, Gobbers, Sneakers, Mummy Greenies, Hiders, and Creepers to create his army. And what's worse is the fact that half the percentage of these ghosts are either shielded, strong, or equipped with a weapon of some form. The combination of these three types of ghosts and the normal ghosts are set to, if not stopped quick enough, spell out the very destruction of Evershade Valley and the world.

History
The Treacherous Mansion is an abandoned museum positioned right in the middle of a giant ravine, which becomes cut off from land access after Luigi reaches the front steps. According to E. Gadd, the mansion contains artifacts and items from Evershade Valley and beyond making it the most "precious" of the mansions. The Mansion is slightly changed to a more spooky look after King Boo arrives. It is called the Treacherous Mansion as it could collapse into the ravine below. It however does not at any point in the game.