Chin Piece

Gol D. Roger, a man referred to as the "Pirate King," is set to be executed by the World Government. But just before his demise,
he confirms the existence of a great treasure, the Chin Piece, located somewhere within the vast ocean known as the Grand Line.
Announcing that Chin Piece can be claimed by anyone worthy enough to reach it, the Pirate King is executed and the Great Age of Pirates begins.