The Last Hope Diamond is a priceless diamond owned by Mrs. Vandereel.
The Last Hope Diamond is a gemstone on a gold necklace.
It was said to contain the curse of the Red Skull. The curse was supposedly carried over to whichever owner purchased it. After wealthy socialite, Mrs. Vandereel, bought the diamond, the Red Skull attacked, stealing the necklace from around her neck in her own home. She hired Mystery Inc. to solve the mystery. The gang stopped him, after tracking him to the town's graveyard, and unmasked Vandereel's own butler, Stuyvesant, who swore revenge.
The New Scooby-Doo Mysteries
Many years after the first incident, Mrs. Vandereel (still wearing the diamond) appeared at a reunion show celebrating Scooby-Doo's birthday. During this show, the Red Skull struck once again, stealing the diamond in plan sight of everyone in the television studio. After being hounded by the Red Skull through the inside and roof of the station, they managed to get the diamond back again.