Keep in mind that you can have only one Mega-Evolved Pokémon at a time. Please note that Shadow and Clone Pokémon cannot be Mega Evolved. After you’ve Mega Evolved a Pokémon, the Mega Energy required to Mega Evolve that specific Pokémon will decrease from then onward. You can Mega Evolve any of your Venusaur, Charizard, Blastoise, and Beedrill once you have enough of their corresponding Mega Energy! Some of these Pokémon are appearing in Mega Raids too.
It seems the faster you defeat a Raid Boss, the more Mega Energy you’ll receive for that Pokémon. You can collect this mysterious substance by completing Mega Raids, which are Raid Battles that feature Mega-Evolved Pokémon. Select Pokémon can Mega Evolve using a newly discovered resource called Mega Energy. What we know so far about Mega Evolution in Pokémon GO
After some research, Professor Willow has documented some notable differences in how Mega Evolution works in the world of Pokémon GO. It appears Mega Evolution has made its way to the world of Pokémon GO! It was observed in some regions, including the Kalos region, that certain Pokémon could reach an additional Evolutionary stage and gain incredible power for a limited time in battle.
