Dream World art of Everstone
Everstone is an item that prevents Pokémon from evolving when it is held. In the games, Everstones are useful as they remove the hassle of having to cancel the evolution of a Pokémon each time it levels up past the level where it evolves (like when you don't want a Pokémon with high friendship to evolve or meeting the right conditions). In the Generation IV games, it prevents evolutions during trades.
Also, an evolved Pokémon does not learn new moves as quickly anymore.
One should note it is unnecessary for Pokémon that evolve via Evolution Stones (like Pikachu) to hold one, however it is useful for Pokémon, like Eevee or a female Snorunt that can evolve into two or more different forms.
This item can also be used in Breeding. When held by a female Pokémon, the chances of passing that Pokémon's Nature onto the Pokémon within the Egg increases by 50%.
