The Odd Keystone is a special item in the Pokémon series, particularly in the games Pokémon Diamond, Pearl, and Platinum. It is used to unlock the Distortion World, a unique area where players can encounter the legendary Pokémon Giratina. The Odd Keystone resembles a small stone with a peculiar design and is often found in specific locations throughout the game. To use the Odd Keystone, players must place it in a specific spot, usually near a Hallowed Tower. This action allows access to the Distortion World, where gravity behaves differently, and players can solve puzzles to progress. The Odd Keystone is essential for those looking to complete their Pokédex and experience the game's unique storyline.