When you play Magcargo from your hand to evolve your Active Pokémon, you may discard the top 3 cards of your deck and and then shuffle 3 basic Energy cards from your discard pile into your deck. If you do, your opponent does the same.

Crushing Lava40+

You may discard a Fire or Fighting basic Energy card attached to Magcargo. If you discard a Fire Energy card in this way, the Defending Pokémon is now Burned. If you discard a Fighting Energy card in this way, this attack does 40 damage plus 20 more damage.