Does 10 damage times the number of damage counters on Donphan.
10×
Rapid Spin
If your opponent has any Benched Pokémon, he or she chooses 1 of them and switches it with his or her Active Pokémon, then, if you have any Benched Pokémon, you switch 1 of them with your Active Pokémon. (Do the damage before switching the Pokémon.)
