Key Stone

The Key Stone is a key item introduced in Generation VI that is used along with a Pokémon holding their respective Mega Stone in order to Mega Evolve. They are typically embedded in a personal accessory worn by the Trainers.

Known Trainers with a Key Stone

Games

Calem's Mega Ring (as the player character or rival, uses on Absol)
Serena's Mega Ring (as the player character or rival, uses on Absol)
Brendan's Mega Bracelet (as the player character or rival)
- Brendan's Mega Cuff (as the player character during contests)
May's Mega Bracelet (as the player character or rival)
- May's Mega Charm (as the player character during contests)
Wally's Mega Pendant (uses on Gallade)
Korrina's Mega Glove (uses on Lucario)
Lisia's Mega Tiara (uses on Altaria)
Lysandre's Mega Ring (uses his specially invented cybernetic Mega Ring on Gyarados)
Maxie's Mega Glasses (uses on Camerupt)
Archie's Mega Anchor (uses on Sharpedo)
Diantha's Mega Charm (uses on Gardevoir)
Steven Stone's Mega Stickpin (uses on Metagross)
Zinnia's Mega Anklet (uses on Salamence)

Anime

Main

Brock's Mega Necklace.
Misty's Mega Hairband.
Ash's Mega Glove.
Roy's Mega Ring.

Brock's Mega Necklace (uses on Steelix)
Misty's Mega Hairband (uses on Gyarados)
Ash's Mega Glove (uses on Lucario)
Roy's Mega Ring (uses on Lucario)

Recurring

Meyer/Blaziken Mask's Mega Belt.
Alain's former Mega Ring.
Diantha's Mega Charm.
Korrina's Mega Glove.
Gurkinn's Mega Glove.
Steven Stone's Mega Stickpin.
Professor Sycamore's Key Stone.
Malva's Mega Necklace.
Lysandre's Mega Ring.
Wulfric's Mega Locket.
Trevor's Mega Camera.
Sawyer's Mega Bookmark.
Gozu's Mega Dog-Tag Necklace.
Ilima's Mega Wrist Band.
Gurkinn's Mega Beard Band.
Alain's current Mega Ring.
Cynthia's Mega Lip Balm.

Meyer's Mega Belt (uses on Blaziken)
Alain's former Mega Ring (uses on Charizard - Mega Charizard X)
Diantha's Mega Charm (uses on Gardevoir)
Korrina's Mega Glove (uses on Lucario)
Gurkinn's Mega Glove (uses on Lucario)
Steven Stone's Mega Stickpin (uses on Metagross)
Professor Sycamore's Key Stone (uses on Garchomp)
Lysandre's Mega Ring (uses on Gyarados)
Malva's Mega Necklace (uses on Houndoom)
Wulfric's Mega Locket (uses on Abomasnow)
Trevor's Mega Camera (uses on Charizard - Mega Charizard Y)
Sawyer's Mega Bookmark (uses on Sceptile)
Gozu's Mega Dog-Tag Necklace (uses on Aggron)
Ilima's Mega Wrist Band (uses on Kangaskhan)
Gurkinn's Mega Beard Band (uses on Alakazam)
Alain's current Mega Ring (uses on Charizard - Charizard X)
Cynthia's Mega Lip Balm (uses on Garchomp)
Uruto's Mega Ring (uses on Sableye)

Minor

Red's Key Stone.
Astrid's Mega Earring.
Remo's Mega Parasol.
Siebold's Mega Buckle.
Mabel's Mega Staff.
A Trainer's Mega Watch.
A Trainer's Mega Turban.
A Trainer's Mega Puppet.
Kimia's Mega Bracelet.
Drasna's Mega Bracelet.
Lisia's Mega Tiara.

Red's Key Stone (uses on Charizard - Mega Charizard X)
Astrid's Mega Earring (uses on Absol)
Remo's Mega Parasol (uses on Garchomp)
Siebold's Mega Buckle (uses on Blastoise)
Mabel's Mega Staff (uses on Mawile)
A Trainer's Mega Watch (uses on Venusaur)
A Trainer's Mega Turban (uses on Alakazam)
A Trainer's Mega Puppet (uses on Banette)
Kimia's Mega Bracelet (uses on Gardevoir)
Drasna's Mega Bracelet (uses on Altaria)
Lisia's Mega Tiara (uses on Altaria)

Trivia

In the games, each type of Key Stone also exists as items in the game data for their names to be used as text when the Trainers Mega Evolve their Pokémon. Except for the obtainable types, Mega Cuff, and Mega Charm, those Key Stones' Bag sprites are question marks ().