Make sure you are connected to the internet, click Mystery Gift, and receive the gift via Internet.
Diancie is available for players of Omega Ruby and Alpha Sapphire and, unfortunately, not available for owners of X and Y.
Diancie is a Rock and Fairy type Pokémon, meaning that Diancie should stay away from Steel, Water, Grass, and Ground type Pokémon. Diancie comes with the ability Clear Body, which prevents opponents from lowering Diancie’s stats.
Diancie also comes holding a Rare Candy and has the following moveset: Diamond Storm, Moonblast, Protect, Dazzling Gleam.
Once you get Diancie, you will receive the Pokémon’s Mega Stone the next time you enter a Pokemon Center.
Will you be getting Diancie, or did you already get the Pokémon when GameStop was giving away their codes? Let me know in the comments!