Shields Down in Pokémon Ultra Sun & Ultra Moon

When its HP becomes half or less, the Pokémon’s shell breaks and it becomes aggressive.

Minior changes to Core Form at half HP or less; Meteor Form prevents major status.

On entering battle and at the end of each turn, Minior changes to Core Form when its HP is at most 50% of maximum, and Meteor Form above 50%. Meteor Form prevents new major status conditions and Yawn, but does not cure an existing status. This Ability cannot be copied, replaced or suppressed.