Primordial Sea
Creates heavy rain, which has all the properties of Rain Dance, cannot be replaced, and causes damaging Fire moves to fail.
Full effect
When this Pokémon enters battle or gains this ability, the weather becomes heavy rain. Heavy rain has all the properties of Rain Dance and also causes damaging Fire moves to fail. Heavy rain ends when this Pokémon leaves battle or loses this ability, or when this ability is nullified. The weather cannot otherwise be changed except by the effects of Delta Stream and Desolate Land. Air Lock and Cloud Nine will prevent the effects of heavy rain, including allowing Fire moves to work, but will not allow the weather to be changed.
In game description
The Pokémon changes the weather to nullify Fire-type attacks.
Using Primordial Sea in Cobblemon
Abilities are passive and always active, so Primordial Sea 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.