Diabolos, King of the Abyss [FOTB-EN061] Secret Rare ARC054-R Set: Dark Revelation Volume 4

Set: Dark Revelation Volume 4 Card type: Effect Monster Rarity: Rare Attack: 2400 Defense: 1000 You can discard 1 card to change the ATK of 1 face-up monster to 2000 until the End Phase of this turn

You can only use this effect of "Heavymetalfoes Electrumite" once per turn

also it cannot be destroyed by battle

whenever an attack deals damage to a hero this turn

While any co-linked "Knightmare" monsters are on the field

Diabolos, King of the Abyss [FOTB-EN061] Secret Rare ARC054-R Set: Dark Revelation Volume 4Set: Force of the Breaker Card type: Effect Monster Rarity: Secret Rare Attack: 2800 Defense: 1000 This card cannot be Special Summoned. If you Tribute Summon this card, the Tributes must be DARK. This card cannot be Tributed by a card's effect. During your opponent's Draw Phase, before their draw, look at the top card of their Deck, then put that card on the top or the bottom of their Deck.