An Everstone is a held item that can be given to a Pokémon to prevent it from evolving. When held by a breeding Pokémon, its Nature is guaranteed to be passed on to its offspring. It can be obtained as a tier 1 special drop.
Before Pixelmon Mod, this item could be crafted and could be used to craft other items. These recipes were removed due to items being easy to obtain.
Everstones could also be used to make Rock Gems.