I've been playing Pokemon X for a while now, and about a month ago I caught myself a Mewtwo (score!) after I caught it, I found a Mewtwonite X. I decided to put Mewtwo in my party, alongside my Delphox, Xerneas, Raichu, Talonflame and Blastoise, and that's when a guy challenged me to a battle. I thrashed him (of course) but I found it strange that after I Mega Evolved my Blastoise, I couldn't Mega Evolve my Mewtwo during the same battle… Anybody know why this is?
Why only one Mega Evolution
pokemon-sixth-generationpokemon-x-y
Related Solutions
In Lumiose City there is a "Stone Emporium" that sells...stones.
If you go in, there's usually only a clerk that sells regular stones (Fire, Leaf, Sun, etc.). However, to the left of the clerk there is a man who does sell the Mega Evolution stones.
Note, his prices are tremendously expensive, if you haven't defeated the Elite Four yet. Defeating the Elite Four and the Champion should move the game into postgame, which drastically cuts down the prices for the stones.
Here are the stones he sells:
Main Game (before Elite Four)
- Charizardite X/Y - 1,000,000
- Venusaurite - 1,000,000
- Blastoisenite - 1,000,000
Post Game (after Elite Four)
- Charizardite X/Y - 150,000
- Venusaurite - 150,000
- Blastoisenite - 150,000
According to the Pokemon Guide, pointed out by BenBrocka, the price can get significantly lower based on how "stylish" you become:
The Pokemon that have mega evolutions at the moment are somewhat arbitrary, in my opinion. Notably the only starters on the list are the Kanto starters (one of which has TWO versions) and Blaizken, and there are no new sixth generation Pokemon with a mega evolution! According to Serebii this is the current list (and this is believed to be final at this point, as there are no other known mega stones).
- Venusaur
- Charizard (two formes, X and Y)
- Blastoise
- Alakazam
- Gengar
- Kangaskhan
- Pinsir
- Gyarados
- Aerodactyl
- Mewtwo (two formes, X and Y)
- Ampharos
- Scizor
- Heracross
- Houndoom
- Tyranitar
- Blaziken
- Gardevoir
- Mawile
- Aggron
- Medicham
- Manectric
- Banette
- Absol
- Garchomp
- Lucario
- Abomasnow
Note that most mega evolutions have different abilities, and a few even change their typing!
Best Answer
It's a built-in game mechanic. Per the wiki: