Multiscale
Halves damage taken from full HP.
Full effect
This Pokémon takes half as much damage when it is hit having full HP.
In game description
Reduces the amount of damage the Pokémon takes while its HP is full.
Pokemon with Multiscale
Using Multiscale in Cobblemon
Abilities are passive and always active, so Multiscale 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.