Rocket's Sneasel ex 103

Before doing damage, you may switch 1 of your opponent's Benched Pokémon with the Defending Pokémon. If you do, this attack does 10 damage to the new Defending Pokémon. Your opponent chooses the Defending Pokémon to switch. Damage: 10

Does 30 damage plus 10 more damage for each of your Darkness Pokémon in play. Damage: 30+