Mementoral Tecuhtlica, the Netherskull Dragon
Cannot be Normal Summoned/Set. Must be Special Summoned (from your hand or GY) by shuffling 5 other "Memento" monsters with different names from your hand and/or GY into the Deck or Extra Deck. If you control no other monsters, this card can attack all your opponent's monsters once each. Once per turn, if your opponent activates a card or effect (except during the Damage Step): You can Special Summon 1 "Memento" monster from your hand or GY.