20TH-JPC09 黒・魔・導・連・弾(ブラックツインバースト) Black Twin Burst (Dark Magic Twin Burst)
Normal Spell Card
You can only activate a card with this card’s name once per turn.
(1) Target 1 “Dark Magician” you control; until the end of the turn, that monster gains ATK equal to the total ATK of all “Dark Magician Girl” on the field and in both players’ GY.

Source