Topple the armor and recover the last Dark Moon piece
Enter the Terrace portal and approach the Dark Moon piece to begin the Tough Possessor fight. The Possessor controls suits of armor. Bait their steps onto the floor rugs, then pull the rugs away to knock them down and expose the ghost. Stun and vacuum the Possessor, filling the Power Surge to remove its protection.
The next phase adds more armor. Keep moving until their feet are positioned over the rugs, and avoid pulling too early while one suit is still off the fabric. After the second exposure, the Possessor takes over a giant suit. Both feet need to be over the rugs. Pull one rug to stagger it, then reach and pull the other before it regains balance. Capture the Possessor after the third exposure and collect the final Dark Moon piece. This completes the five-mansion Possessor hunt, but Mario still needs rescuing in A Nightmare to Remember.