Mega Stones

A Mega Stone (Japanese: メガストーン Mega Stone) is a type of held item introduced in Pokémon X and Y. It allows Pokémon to Mega Evolve. According to Professor Sycamore, Mega Stones are the results of Evolutionary stones being irradiated by the power of the Legendary Pokémon XerneasX or YveltalY. In Pokémon Omega Ruby and Alpha Sapphire, it has been revealed that Mega Stones are also periodically created from meteorites that fall down from the sky in a form of green light.