Stealth Beast, Tamahagane "Metsu"

:When this unit is placed on or , bind up to one card from the top of your deck face down. (Only the owner may look at their cards bound face down) : 1 When a dominated unit attacks during your turn, you may pay the cost. If you do, choose one face down card from your bind zone, and you may put it into your hand. If you do, this unit gets +10000 until end of turn.