Gaia Dragon, the Thunder Charger (AP07-EN001) - Astral Pack 7 Unlimited

2 Level 7 monsters
You can also Xyz Summon this card by using a Rank 5 or 6 Xyz Monster you control as the Xyz Material. (Xyz Materials attached to that monster also become Xyz Materials on this card.) If this card attacks a Defense Position monster, inflict piercing battle damage to your opponent.