Pocket Monsters XY: Hakai no Mayu to Diancie

In the Diamond Domain, a subterranean region inhabited by many Carbink, Diancie rules as the Mythical Pokémon. The Heart Diamond, essential to the domain's survival, is deteriorating, and Diancie lacks the strength to create a replacement. Seeking aid from Xerneas, Diancie encounters thieves who desire to exploit its diamond-making abilities. In their attempt, the thieves awaken Yveltal from its cocoon. Ash and his companions must assist Diancie in unlocking its full potential, halt Yveltal's destructive actions, and prevent the downfall of the Diamond Domain.