Pokemon XY Mega 3-Movie Collection contains Pokemon Movies 17-19 - Diancie and the Cocoon of Destruction, Hoopa and the Clash of Ages, and Volcanion and the Mechanical Marvel.

Pokémon the Movie: Diancie & the Cocoon of Destruction
In the underground Diamond Domain, where many Carbink live, the Mythical Pokémon Diancie serves as ruler. The Heart Diamond that sustains the land is beginning to fall apart, and Diancie is not yet strong enough to create a new one. While seeking help from the Legendary Pokémon Xerneas, Diancie encounters a group of thieves who want to take control of its diamond-producing power–and who awaken the Legendary Pokémon Yveltal from its cocoon in the process! Can Ash and his friends help Diancie discover its true power, stop Yveltal’s rampage, and save the Diamond Domain?

Pokémon the Movie: Hoopa & the Clash of Ages.
The Mythical Pokémon Hoopa is the star of Pokémon the Movie: Hoopa and the Clash of Ages! When Ash, Pikachu, and their friends visit a desert city by the sea, they meet the Mythical Pokémon Hoopa, who has the ability to summon things—including people and Pokémon—through its magic ring. After a scary incident, they learn a story about a brave hero who stopped the rampage of a terrifying Pokémon long ago. Now, the threat that has been bottled up for years is in danger of breaking loose again! Can Ash help his new friend overcome the darkness within...or will a dangerous secret erupt into a clash of legends?

Pokémon the Movie: Volcanion & the Mechanical Marvel.
In this latest cinematic adventure, Ash meets the Mythical Pokémon Volcanion when it crashes down from the sky, creating a cloud of dust—and a mysterious force binds the two of them together! Volcanion despises humans and tries to get away, but it’s forced to drag Ash along as it continues its rescue mission. They arrive in a city of cogs and gears, where a corrupt minister has stolen the ultimate invention: the Artificial Pokémon Magearna, created 500 years ago. He plans to use its mysterious power to take control of this mechanical kingdom! Can Ash and Volcanion work together to rescue Magearna? One of the greatest battles in Pokémon history is about to unfold!