Necklace (Paper Mario: The Thousand-Year Door)
From the Super Mario Wiki
The Necklace is one of Flurrie's accessories in Paper Mario: The Thousand-Year Door. She never leaves the house without her Necklace. The Shadow Sirens come across it in Boggly Woods, and Mario must defeat them to take it back from them. When Mario returns the Necklace to Flurrie, she thanks him and joins Mario's party.