Mega Evolution is a special kind of transformation that affects certain Pokémon. It is an extra evolution that brings about a change in appearance, a boost to stats in battle, and occasionally a new ability, but only for the duration of a battle or until that Pokémon faints. Only one Pokémon can be Mega Evolved during a battle, and if it is knocked out, it reverts to its original form and cannot be evolved again in the same battle.
Mega Evolution can only be activated when the trainer has a Key Stone and the Pokémon is holding its specific Mega Stone. Vaeryn will give the player the Mega Bracelet as their Key Stone and one free Mega Stone that matches one of their party Pokémon upon defeating him at the Snowbank Town Gym. Prior to patch 1.0.2, this was the only way to obtain an Unidentified Fallen Object to Mega Evolve S51-A; as of the latest release, all usable Mega Stones can be found throughout Tandor (though receiving one for free can still be advantageous).
Certain Pokémon in Tandor are capable of Mega Evolution. These Pokémon are: