An event is currently running in Pokemon Omega Ruby & Alpha Sapphire that allows you to get your grubby little mitts on Diancie.
You'll have to be quick though because it runs out on Monday, July 27th.
Simply tap on 'Mystery Gift' on the main menu, hit 'Receive Gift', and then opt for 'Get Via Internet' to unlock your very own Diancie, who isn't currently available in the wild.
Diancie uses the abilities Diamond Storm, Moonblast, Dazzling Gleam, and Protect.
Bear in mind that the event is currently only available in Europe and Australia, but is set to start in the US later today.
We gave Pokemon Omega Ruby & Alpha Sapphire a Gold Award at review, and said that it "brings back and adds some great features, but not without cutting out some of the standards set in Pokémon X and Y".