The official site has confirmed the Mega Evolutions of Ampharos, Absol and Mawile and provided clearer pictures.
WhenAmpharosMega-Evolves, apparently the red orbs on its body emit a strong light.
Mega Mawileincreases its Defense and Special Defense.
Our Pokedex has been updated with the latest details. For now, the Mega Evolutions are listed as forms. Based on currently-known information, Mega Evolution works in the same way as an in-battle form change.
A few other additions we havent yet already mentioned in news are a new attack,Nuzzle(learnt by Dedenne), and a new Ability,Cheek Pouch(possessed by Dedenne and Bunnelby).
A new trailer for Mega Evolutions has also been released:
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