During their travels through the Unova region, Ash and his friends Iris and Cilan arrive in Eindoak Town, built around a castle called the Sword of the Vale. The three Trainers have come to compete in the town's annual battle competition, and Ash manages to win with some unexpected help from the Mythical Pokémon Victini! It turns out Victini has a special bond with this place…

Long ago, the castle watched over the Kingdom of the Vale, and the partnership between Victini and the king protected the people who lived there. But that kingdom has since vanished into memory, leaving behind powerful relics and ancient Pokémon. Damon, a descendant of the People of the Vale, is trying to restore the lost kingdom with the help of his Gothitelle. His quest has taken him to the far reaches of the frozen tundra, and he has convinced the Legendary Pokémon Zekrom to help him seek his ideals!

Damon plans to trap Victini and harness its power, and as that plan gets under way, the entire town of Eindoak faces disaster! Can Ash awaken the Legendary Pokémon Reshiram to help him stop Damon and save Victini? The greatest adventure in Pokémon history approaches!