If held by an Abomasnow, allows it to Mega Evolve into Mega Abomasnow 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 Abomasnow a Abomasite or remove a Abomasite from Abomasnow.
Outside of battle
If held by an Abomasnow, allows it to Mega Evolve into Mega Abomasnow when it performs a Spectacular Talent during a Pokémon Contest Spectacular while its Trainer has a Key Stone. Abomasnow will remain a Mega Abomasnow until the Talent Round ends.
An Abomasite appeared in A Real Icebreaker!, worn by Wulfric's Abomasnow. The Frost Tree Pokémon wears its Mega Stone on its chest, revealing it only when it's about to Mega Evolve. Wulfric used it in Ash's rematch against him to battle Ash's Greninja.
