First introduced in Pokémon X and Y, certain Pokémon are capable of Mega Evolving during battle. Similar to normal evolution, they can benefit from increased stats and even a different Type combination. However, Mega Evolution isn’t permanent and the effects disappear after the battle–or if the Pokémon is KO’d.
To Mega Evolve, you need two things. First, you need a Key Stone, which is given to you before you challenge the eighth Gym. Next, you need the corresponding Mega Stone for your Pokémon. You get the Mega Stones for the original Kanto starters at the same time as the Key Stone, while the rest are relegated to the post-game.
If a Pokémon is capable of Mega Evolving–and once the conditions have been met, you can Mega Evolve by selecting the command to the left of a Pokémon’s moves, and then choosing a move as normal. Afterwards, the Pokémon will Mega Evolve as the turn begins, and use their move when it’s their turn.
|Pokémon||Mega Evolution Benefits||Mega Stone Location|
|Venusaur||Increased offence and bulk.||From Blue before the eighth Gym.|
|Charizard||X: Gains Dragon-type and increased offence. Y: Increased special stats.||From Blue before the eighth Gym.|
|Blastoise||Increased offence and bulk.||From Blue before the eighth Gym.|
|Beedrill||Massively increased Attack and Speed.||Indigo Plateau when Champion.|
|Pidgeot||Massively increased Special Attack.||Indigo Plateau when Champion.|
|Alakazam||Increased Special Attack and Speed.||Indigo Plateau when Champion.|
|Slowbro||Massively increased Defence.||Indigo Plateau when Champion.|
|Gengar||Increased Special Attack and Speed.||Indigo Plateau when Champion.|
|Kangaskhan||Increased offence and bulk.||Indigo Plateau when Champion.|
|Pinsir||Gains Flying-type and increased Attack and Speed.||Indigo Plateau when Champion.|
|Gyarados||Flying replaced with Dark and gains Attack and bulk.||Indigo Plateau when Champion.|
|Aerodactyl||Increased Attack and Speed.||Indigo Plateau when Champion.|
|Mewtwo||X: Gains Fighting-type and massively increased Attack. Y: Massively increased Special Attack.||From Green in Cerulean Cave.|