The Necklace of Oros Defenders of the Earth : Season 1 Episode 56

As part of Jedda's coming of age, the Phantom takes her to the Skull Cave to choose a gift from among the family treasures. She is drawn to the mysterious Necklace of Oros, but an evil interdimensional being named Graviton needs the Necklace for his own purposes and will stop at nothing to get it.