If held by a Diancie, allows it to Mega Evolve into Mega Diancie if its Trainer has a Key Stone. Each Trainer can only Mega Evolve one Pokémon per battle.
Unaffected by item negating effects (such as Embargo and Klutz). Item manipulating effects (such as Trick and Fling) cannot give Diancie a Diancite or remove a Diancite from Diancie.
Outside of battle
If held by a Diancie, allows it to Mega Evolve into Mega Diancie when it performs a Spectacular Talent during a Pokémon Contest Spectacular while its Trainer has a Key Stone. Diancie will remain a Mega Diancie until the Talent Round ends.
The player can obtain the Diancite by passing Level 50 on a Mega Diancie escalation battle in Weeks 10 and 11 of the event rotation.
The Diancite was also available as a prize during the Mega Diancie escalation battles prior to the event rotation system. This escalation battle ran on both the Nintendo 3DS and Mobile versions from February 9 to 23, 2016; August 23 to September 6, 2016; April 11 to 25, 2017; August 22 to September 5, 2017; and December 12 to 26, 2017.
The Diancite enables the following Mega Evolutions:
Removes barrier-covered Pokémon / disruptions (max 10) and damages the foe. Does +100 damage per barrier-covered icon erased. Formerly, the description was "Erases Pokémon that are covered by a barrier (max 10)." and did not deal extra damage until Version 1.3.28 (3DS)/1.9.1 (Mobile).
