Mythical Beast Medusa [SR08-EN009] Common

Each time a Spell Card is activated, place 1 Spell Counter on this card when that Spell resolves. Once per turn, during the Battle Phase (Quick Effect): You can remove 2 Spell Counters from your field, then target 1 face-up monster on the field; its ATK/DEF become half its current ATK/DEF until the end of this turn.