Spadassin De La Vie Potartiste MP17-FR064

If your opponent controls a Special Summoned monster and they control at least as many monsters as you do, you can Special Summon this card (from your hand). Once per turn, you can target 1 face-up monster on each field; until the end of this turn, the opponent's monster loses ATK equal to this card's ATK, and if it does, the monster you control gains ATK equal to this card's ATK.