mega mewtwo x
With Mewtwonite X, Mewtwo's body becomes more muscular and its eyes turn blue. It becomes a dual Psychic/Fighting-type, its physical attacks become much stronger, and its speed increases whenever it flinches.
Using Mewtwonite Y will make Mewtwo evolve into Mega Mewtwo Y instead.
This tag implicates mewtwo (learn more).