Swordhorn Dragon, Scathrex

:[Choose one of your rear-guards with "Rex" in its card name, and retire it] When this unit attacks a vanguard, you may pay the cost. If you do, draw a card, and this unit gets +3000 until end of that battle. :[Choose a card from your hand, and bind it face up] When this unit is placed on or , you may pay the cost. If you do, choose one of your other rear-guards with "Rex" in its card name, that unit and this unit get +2000 until end of turn.