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25th Anniversary Tin: Dueling Mirrors

“If 10 or more cards and/or effects have been activated during this turn: Special Summon this card as an Effect Monster (Cyberse/DARK/Level 10/ATK 3000/DEF 3000) (this card is also still a Trap), but Set it in your Spell & Trap Zone during your End Phase. Once per turn, when your opponent activates a card or effect, while this card is in your Monster Zone (Quick Effect): You can destroy as many cards your opponent controls as possible, then Set this card in your Spell & Trap Zone.”