As they were searching the island, the crew of the Straw Hats came across an old man who seemed to know more about the curse than anyone else. He told them that the sorcerer who had cursed the island had died long ago, but that his curse had lingered on.
The old man explained that the curse was linked to an ancient power source that had been hidden on the island. He told them that the power source had been used by the sorcerer to create the curse, and that it was the only way to break it.
The crew of the Straw Hats listened intently, and they realized that this was the key they had been searching for. They asked the old man if he knew where the power source was hidden, and he told them that it was deep within a cave on the other side of the island.