Late last year hackers came into the world of Pokemon X & Y when players found three Pokemon that are not typically found in the game. These were Diancie, Hoopa and Volcanion.
The Pokemon community eventually spoke up after the discovery and confirmed that Diancie was making its way into Pokemon X & Y. It seems that the Pokemon is very rare and is the fairy/rock type and it cannot be found in open play.
The community said that the Pokemon would be making a special arrival in an event in Pokemon X & Y. Diancie was thought to be a legendary Pokemon but we have heard that it is in fact an evolved Carbink. How the evolution could happen is not known. Perhaps it will be a special evolution like Cherrim or Castform or it could be a mega evolution.
For now Pokemon fans will have to wait if they want to catch Diancie while the event happens and the Pokemon is revealed.