From Bulbapedia, the community-driven Pokémon encyclopedia.
Terraki-Mewtwo is the name of the deck used by Shuto Itagaki, the Junior Division Champion in the 2012 World Championships. It is one of the four 2012 World Championships Decks, released in November 2012. Each deck comes packaged with a 2012 World Championships Booklet, Deck Box, and Special Pin. Each card features a silver border, Itagaki's signature, and limited edition 2012 World Championships back. None of the cards are tournament legal.
Shuto Itagaki's Terraki-Mewtwo deck shows all the cunning and strategy expected in a World Champion, focusing not only on speed and damage-dealing, but also on reducing the effectiveness of the opposition! A streamlined Pokémon line-up featuring only Mewtwo-EX and Terrakion ensures that there is plenty of space for cards to help source Energy from the deck for heavy hits, while Ruins of Alph will make sure that not only is Resistance non-existent…it's impossible!