If held by an Absol, allows it to Mega Evolve into Mega Absol 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 Absol a Absolite or remove a Absolite from Absol.
Outside of battle
If held by an Absol, allows it to Mega Evolve into Mega Absol when it performs a Spectacular Talent during a Pokémon Contest Spectacular while its Trainer has a Key Stone. Absol will remain a Mega Absol until the Talent Round ends.