Where can you find Mewtwo and the Mewtwonites in Pokémon X & Y?

Question

Is it possible to find Mewtwo in Pokémon X? if so, where?

Answer 1

In Pokemon Village, there is a cave called the Unknown Dungeon. Mewtwo will be in there, but you can only enter after you defeat the Champion. After you catch it there will be a Mewtwonite -- either X or Y depending on your game version.
Here's a video of Terminus Cave: http://www.youtube.com/watch?v=FvUbFX36SVg

Comments

It is really called the Unknown Dungeon FYI.

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Terminus cave is where you find Zygarde.

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beat the elite 4