Perish Body
When hit by a move that makes direct contact, the Pokémon and the attacker will faint after three turns unless they switch out of battle.
Full effect
When the Pokémon with Perish Body is hit with a contact move, both the attacker and the Pokémon with Perish Body will faint in three turns.
In game description
When hit by a move that makes direct contact, the Pokémon and the attacker will faint after three turns unless they switch out of battle.
Pokemon with Perish Body
Using Perish Body in Cobblemon
Abilities are passive and always active, so Perish Body 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.