Innards Out is an ability introduced in the seventh generation that deals damage to the attacker after the user is defeated. It is the signature ability of Pyukumuku.
When a Pokémon with this Ability faints, it deals damage to its opponent equal to the amount of HP it had left before being fainted through direct damage. Damage through weather, status conditions and field hazards do not trigger this ability. This ability has no effect outside of battle.