Elemental Hero Thunder Giant [EHC2-EN004] Secret Rare Equip Spell if you have no cards

if you have no cards in your Spell & Trap Card Zone: You can detach 1 Xyz Material from this card

and destroy all those monsters with 1500 or more ATK

You can only activate 1 "Spellbook of Fate" per turn

except with a card effect

Elemental Hero Thunder Giant [EHC2-EN004] Secret Rare Equip Spell if you have no cardsSet: Elemental Hero Collection 2 Card type: Fusion Effect Monster Rarity: Secret Rare Attack: 2400 Defense: 1500 "Elemental HERO Sparkman" + "Elemental HERO Clayman" This monster cannot be Special Summoned except by Fusion Summoned. Once per turn, during your Main Phase, by discarding 1 card from your hand, select and destroy 1 face up monster on the field with an original ATK that is less than the ATK of this card.