Key Stone/Anime/Main series

In Mega Evolution Special I, Alain was seen wearing a Mega Ring similar to that of the protagonists of Pokémon X and Y. He uses it to Mega Evolve his into Mega Charizard X. In Mega Evolution Special II, it was revealed that he received it from Lysandre. After the Team Flare crisis, Alain gave his Mega Ring to Professor Sycamore to be used for his research.

In the same episode, Astrid was shown wearing her Key Stone as an earring on her right ear, while Remo had his Key Stone embedded into the tip of the umbrella that he carries with him. Siebold, a member of the Kalos Elite Four, was seen wearing his Key Stone in his necktie. Astrid's Key Stone made a brief reappearance during the opening credits of Diancie and the Cocoon of Destruction.

In The Bonds of Evolution!, Diantha tapped into the power of her Mega Charm to Mega Evolve her, giving it the power to break free from 's clutches. The Mega Charm has also been seen during Diantha's subsequent appearances.

In Mega Revelations!, Korrina was shown wearing her Key Stone in her Mega Glove, having received it from her grandfather. However, her lacked the Lucarionite, meaning that she wasn't able to use it yet. After obtaining a Lucarionite in The Cave of Trials!, she was soon able to use her Key Stone in order to Mega Evolve her Lucario.

Another Key Stone appeared in The Aura Storm!, under the ownership of Gurkinn, who uses it to Mega Evolve his own Lucario. Similar to Korrina, he wears it in a glove on his left hand.

A Key Stone possessed by Mabel appeared in The Bonds of Mega Evolution!. Embedded in her walking stick, she uses it to Mega Evolve her into Mega Mawile.

In Diancie and the Cocoon of Destruction, a diamond Diancie had created and given to earlier caused it to Mega Evolve, acting as a Key Stone. At the end of the movie, Bonnie returned the diamond to Diancie.

Mega Evolution Special II featured and his Mega Stickpin. Alain was able to recognize the Key Stone on the 's person, leading him to challenge Steven to a battle.

In the same episode, a giant Key Stone was discovered by Steven and Alain. While Lysandre's scientists were inspecting it, appeared and used the Key Stone's power to Mega Evolve into Mega Rayquaza. Soon after, it disappeared along with the chaos created by Rayquaza's. The stone reappeared in Mega Evolution Special III, along with Mega Rayquaza. It was eventually taken away by Lysandre's submarine to be studied at the Lysandre Labs.

In Garchomp's Mega Bond!, it was revealed that Professor Sycamore had found a Key Stone along with a piece of Garchompite. In the same episode, it was revealed that Blaziken Mask keeps his Key Stone embedded in his belt buckle.

Multiple Key Stones appeared in Mega Evolution Special IV. A Trainer with a has his Key Stone inside of a pocket watch, a  Trainer wears his Key Stone on his turban, Malva carries her Key Stone in a necklace, a  Trainer has his embedded on his Banette puppet, and Lysandre has his Key Stone embedded in a Mega Ring he wears on his left hand.

A Key Stone belonging to Wulfric appeared in A Real Icebreaker!. The Snowbelle City Gym Leader keeps his Key Stone inside of the locket he wears around his neck, and uses it to Mega Evolve his.

In A League of His Own!, was revealed to have a Key Stone embedded on his camera's shutter button. With it, he is able to Mega Evolve his into Mega Charizard Y.

In Valuable Experience for All!, Sawyer was revealed to have a Key Stone attached on the end of his notebook latch. He uses it to Mega Evolve his. In The First Day of the Rest of Your Life!, Sawyer revealed that he received his Key Stone from Steven.

A Key Stone held by Kimia appeared in Volcanion and the Mechanical Marvel, wearing it on a bracelet around her left wrist. She uses it to Mega Evolve her Gardevoir.

A Key Stone belonging to, located on her hair band, and a Key Stone belonging to , located on a necklace under his shirt, appeared in When Regions Collide!.

In The Prism Between Light and Darkness!, Gozu was revealed to own a Key Stone embedded inside a dog-tag necklace that is kept hidden under his Team Rocket uniform. He uses it to Mega Evolve his.