Pokémon The Movie XY: Hakai no Mayu to Diancie

A subterranean nation known as Diamond Ore Country is home to the Carbink, living harmoniously under the rule of princess Diancie. The region's energy comes from the Sacred Diamond, a massive gem that only the princess can produce. However, Diancie lacks the ability to create a new diamond, and the existing one is nearing depletion, threatening the country's survival. Diancie joins forces with Ash and Pikachu to seek out Xerneas, a legendary Pokémon with sacred power. During their journey, they discover a cocoon containing Yveltal, a destructive Pokémon believed to have once caused devastation in Kalos.