Iron Barbs
Damages attacking Pokémon for 1/8 their max HP on contact.
Full effect
Whenever a move makes contact with this Pokémon, the move's user takes 1/8 of its maximum HP in damage. This ability functions identically to Rough Skin.
In game description
Inflicts damage on the attacker upon contact with iron barbs.
Pokemon with Iron Barbs
Using Iron Barbs in Cobblemon
Abilities are passive and always active, so Iron Barbs 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.