Main Observation Room
From the Super Mario Wiki, the Mario encyclopedia
The Main Observation Room is a location in Luigi's Mansion 3, found in the Master Suite of the Last Resort. It is a security room that Hellen Gravely uses to spy on Luigi, especially after he rescues one of the three Toads from a portrait.
It is located in the farthest back corner of the Master Suite behind a King Boo shaped vault that Luigi must open by finding four keys in other rooms of the Master Suite. The room has a heavy security system of lasers like most rooms in the suite that Gravely uses to attack Luigi. There is a hidden room underneath the floor only Gooigi can access to disarm the colored laser grids, although, water periodically flows through this area to sabotage Gooigi's efforts. There is a door hidden behind the screens that gives Luigi access to the Rooftop where King Boo waits.
When Luigi opens the vault, Hellen Gravely angrily blames him for her losing everything, unintentionally exposing her true face in the process. After reapplying her makeup, she turns The Observation Room into an arena and battles Luigi personally.
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