Disguise
Prevents the first instance of battle damage.
Full effect
If this Pokémon is in its Disguised Form and takes damage from a move, it switches to its Busted Form and the damage is prevented. Other effects are not prevented. This ability cannot be copied or replaced. This ability only takes effect for Mimikyu.
In game description
Once per battle, the shroud that covers the Pokémon can protect it from an attack.
Pokemon with Disguise
Using Disguise in Cobblemon
Abilities are passive and always active, so Disguise 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.