Serene Grace
Doubles the chance of moves' extra effects occurring.
Full effect
This Pokémon's moves have twice their usual effect chance. An effect chance is a move's chance to inflict a status ailment, cause a stat change, or make the target flinch in addition to the move's main effect. For example, Flamethrower's chance of burning the target is doubled, but Protect's chance of success and Air Cutter's increased critical hit rate are unaffected. Secret Power is unaffected.
In game description
Raises the likelihood of additional effects occurring when the Pokémon uses its moves.
Pokemon with Serene Grace
Using Serene Grace in Cobblemon
Abilities are passive and always active, so Serene Grace 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.