The "Mist Stone" legend is an urban legend revolving around the 1996 role-playing games Pokémon Red and Blue.
Description
In the early days of the games' lifetimes, rumors spread of a hidden item called a Mist Stone. While many Pokémon evolve via the use of special elemental stones, the Mist Stone was supposedly capable of evolving every Pokémon in the game, including those that were fully evolved or those who didn't normally evolve through any other means.
Players could supposedly find the Mist Stone on Seafoam Island after collecting every other item in that area and then using the Itemfinder device on every title on the island. Of course, experimentation with this method has yet to find any evidence of such a stone existing.