Dragonic Vanquisher "SPARKING"

Thunderstrike 4(Active when your opponent's bind zone has four or more cards):At the beginning of your ride phase, 1 or 1, your opponent chooses a card from his or her drop zone, and binds it face up. : 1 When your G unit , you may pay the cost. If you do, your opponent chooses a card from his or her drop zone, and binds it face up. Then, if the G unit has the thunderstrike ability, your opponent chooses one of his or her rear-guards, retires it, and binds it face up.