War Rock Wento

If your EARTH Warrior monster battles an opponent's monster, during damage calculation (Quick Effect): You can pay 800 LP; your battling monster gains 800 ATK, until the end of this turn. If this card is sent from your Monster Zone to your GY by an opponent's card effect: You can Special Summon 1 Level 5 or higher "War Rock" monster from your hand or Deck. You can only use each effect of "War Rock Wento" once per turn.