Blackwing - Sirocco the Dawn

If your opponent controls a monster and you control no monsters, you can Normal Summon or Set this card without Tributes. Once per turn: You can target 1 face-up "Blackwing" monster you control; until the End Phase, it gains ATK equal to the total ATK of all face-up "Blackwing" monsters currently on the field, except itself. Monsters other than that target cannot attack during the turn you activate this effect.