Choose 1 of your opponent's Pokémon. This attack does 20 damage to that Pokémon. This attack's damage isn't affected by Weakness, Resistance, Pokémon Powers, or any other effects on the Defending Pokémon.
The Defending Pokémon can't retreat as long as Murkrow remains your Active Pokémon. (Benching or evolving either Pokémon ends this effect.)