Pokémon Power: Magma Pool
If Magcargo is your Active Pokémon and moves to the Bench, remove 1 [R] Energy card attached to Magcargo, if any, and attach it to the new Active Pokémon. (You can’t choose an Energy card that you used to pay the Retreat Cost.)
[R][R][R] Lava Flow: 40+
You may discard any number of [R] Energy cards attached to Magcargo when you use this attack. If you do, this attack does 40 damage plus 20 more damage for each [R] Energy card you discarded in this way.
The shell on its back is just skin that has cooled and hardened. It breaks easily with a slight touch.