Pokémon the Movie: Diancie and the Cocoon of Destruction

When Diancie a Pokémon said to create diamond travels to find Xerneas to help her make a heart diamond to save her home, Ash, Serena, Clemont and Bonnie help her to be safe on the way from thieves.
In the underground Diamond Domain, where many Carbink live, the Mythical Pokémon Diancie serves as ruler. The Heart Diamond that sustains the land is beginning to fall apart, and Diancie is not yet strong enough to create a new one. While seeking help from the Legendary Pokémon Xerneas, Diancie encounters a group of thieves who want to take control of its diamond-producing power–and who awaken the Legendary Pokémon Yveltal from its cocoon in the process! Can Ash and his friends help Diancie discover its true power, stop Yveltal’s rampage, and save the Diamond Domain?