The Great Stage
The Great Stage is the fourth floor of The Last Resort in Luigi's Mansion 3. Luigi can access it after having acquired the fourth floor elevator button from Chef Soulfflé and some mice in the Mezzanine. After reaching this floor for the first time, Professor E. Gadd will call Luigi and inform him that he can use the Virtual Boo to instantly warp to the lab from anywhere, as long as he is by himself.
Upon entering the Auditorium, Luigi discovers the red Toad's portrait on the stage where Amadeus Wolfgeist is playing his piano. When he tries to get on the stage, Amadeus notices him and retracts the stairs leading up to the stage, then starts making the chairs levitate and tries hit Luigi with them. Once they have all shattered, he summons Goob ballerinas to go after Luigi. When Luigi captures all of the Goobs, Amadeus possesses his piano and attacks Luigi directly. After capturing Amadeus, Luigi rescues the Toad and obtains the sixth floor elevator button. He delivers Toad to E. Gadd in his lab, and heads up to the sixth floor, Castle MacFrights.