Mordschlag (MP20-EN081) [2020 Tin of Lost Memories]

Equip only to a Normal Summoned/Set monster you control. It is unaffected by your opponent's activated effects of Special Summoned monsters. During damage calculation, if the equipped monster battles an opponent's Special Summoned monster: That opponent's monster loses ATK/DEF equal to the equipped monster's original ATK, during that damage calculation only.