Number C69: Heraldry Crest of Horror

4 Level 5 monsters // When an opponent's monster declares an attack: You can destroy all cards your opponent controls. If this card has "Number 69: Heraldry Crest" as an Xyz Material, it gains this effect. // * Once per turn: You can detach 1 Xyz Material from this card, then target 1 face-up Xyz Monster your opponent controls; this card gains ATK equal to that face-up monster's original ATK, and if it gains ATK this way, this card's name becomes that monster's, and it gains that monster's original effect. These effects last until the End Phase.