絶滅の王

絶滅の王のパワーとタフネスは、それぞれすべての墓地にあるカードの総数に等しい。

Lord of Extinction

Lord of Extinction's power and toughness are each equal to the number of cards in all graveyards.

Double Masters 2022

Amonkhet Remastered

Ultimate Masters

Ultimate Box Topper

If an instant or sorcery spell deals damage to Lord of Extinction or lowers its toughness, that spell is put into its owner's graveyard before state-based actions are performed. That card will raise Lord of Extinction's toughness before the game checks to see if it dies.

The ability that defines Lord of Extinction's power and toughness works in all zones, not just the battlefield. If Lord of Extinction is in your graveyard, it will count itself.