There's a crisis as Pokemon The Movie: Diancie And The Cocoon Of Destruction Opens. Princess Diancie realizes that the Heart Diamond, which provides all the life-giving energy to the Diamond Domain where she lives, is dying. Time has taken its toll, and Diancie is the only one with enough power to create a new Heart Diamond to take its place. The young princess, unsure of herself and aware that she needs the magical assistance of Xerneas, the Life Pokemon, enlists Ash and his Pokemon partners to make the journey with her. It's a treacherous trip. Diancie's reputation as the sole creator of diamonds has made her the target of a series of greedy villains, including the world of Pokemon's Team Rocket, Millis and Arbus, and Riot and Merilyn, all of whom are eager to take her prisoner and use Diancie's talents to enrich their lives. But finding Xerneas and calling upon her great gifts doesn't begin to prepare the heroes for their encounter in the All-Earth Forest with Yveltal, the Destruction Pokemon. It's an all-out battle for the Pokemon's very lives and for the survival of the fragile forest, as well as the Diamond Domain.