When this card is activated: You can add 1 Subterror monster from your Deck to your hand. Once per turn: You can change 1 face-down Defense Position Subterror monster you control to face-up Attack or Defense Position. Once per turn, when an opponent s monster declares an attack: You can change 1 face-down Defense Position Subterror monster you control to face-up Attack or Defense Position, then you can negate the attack. You can only activate 1 The Hidden City per turn.