Once during your turn (before your attack), you may search your discard pile for a Basic Pokémon (excluding Pokémon-ex and Ditto) and switch it with Ditto. (Any cards attached to Ditto, damage counters, Special Conditions, and effects on it are now on the new Pokémon.) Place Ditto in the discard pile.

Does 10 damage plus 10 more damage for each Energy attached to Ditto but not used to pay for this attack's Energy cost. You can't add more than 20 damage in this way.