In a country called Diamond Domain (ダイヤモンド鉱国 Daiyamondo Kōkoku?)[Note 1] lies the powerful Heart Diamond (聖なるダイヤ Seinaru Daiya?, "Holy Diamond"), in which served as the kingdom's source of energy and maintains the Ore Country for centuries. Various Melecie all live in the said country including their princess, the Jewel Pokémon Diancie who created the powerful diamond. However she no longer has the power to control the Heart Diamond and her country is falling into chaos as the diamond's life is falling apart.
One day, she meets with Satoshi and his friends and pleads them to go on a journey to find the Life Pokémon Xerneas in order to restore the Heart Diamond back to life. But standing in her way is the Pokémon of Destruction, Yveltal, who once stole all life in the Kalos Region. During their journey, they are also attacked by Team Rocket, as well as jewel thieves Marilyn Flame and Ninja Riot. They are aided by Millis Steel and her father Argus, travelers who also encounter the Cocoon of Destruction.
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