This specific card, Mega Mewtwo EX, is from the XY Breakthrough expansion set, released in 2015. Mega Evolution is a mechanic introduced in the XY series, allowing certain Pokémon to temporarily transform into a more powerful form during battle. Mega Mewtwo EX is a formidable Psychic-type Pokémon known for its high HP and powerful attacks, making it a sought-after card for both players and collectors.
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