Shields Down
Transforms this Minior between Core Form and Meteor Form. Prevents major status ailments and drowsiness while in Meteor Form.
Full effect
When this Pokémon enters battle and at the end of each turn, if its HP is 50% or above, it changes into Meteor Form; otherwise, it changes into Core Form. In Meteor Form, it cannot be given a major status ailment (though existing ones are not cured), cannot become drowsy from Yawn, and cannot use Rest (which will simply fail). This ability cannot be copied, replaced, or nullified. This ability only takes effect for Minior.
In game description
When its HP drops to half or less, the Pokémon's shell breaks and it becomes aggressive.
Pokemon with Shields Down
Using Shields Down in Cobblemon
Abilities are passive and always active, so Shields Down costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.