Mega Stone are evolutionary stones that allow certain Pokémon to reach their final form for one-evolution families and second/true final form for two-evolution/branch-evolution families.
Each Mega Stone has a "-ite" or "-nite" on the end of it preceded by the related Pokemon's name (Example: Lucario's Mega Stone is called Lucario-"nite", Blaziken's Mega Stone is Blaziken-"ite").
Certain Pokémon will be able to evolve into a Mega form with the use of a Mega Stone, a held object. However this evolution will devolve into to their pre-evolved form at the end of the battle.
- Before Team Robot In Pokemon XY The Series, Princess Anna, Elsa the Snow Queen, and Kristoff each received a Mega Stone from the Grand Pabbie after hearing stories about its mysterious power. The Grand Pabbie tells them to use the stones wisely but warns them that if the stones are placed into the wrong hands, the bonds of both Pokémon and humans will be in grave danger.