Battle Bond

Full effect

Transforms this Pokémon into Ash-Greninja after fainting an opponent. Water Shuriken's power is 20 and always hits three times. This ability cannot be copied or replaced. This ability only takes effect for Greninja.

In game description

When the Pokémon knocks out a target, its bond with its Trainer is strengthened, and its Attack, Sp. Atk, and Speed stats are boosted.

Using Battle Bond in Cobblemon

Abilities are passive and always active, so Battle Bond 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.