Karn's Sylex [Dominaria United]

Set: Dominaria United Type: Legendary Artifact Rarity: Mythic Cost: {3} Karn's Sylex enters the battlefield tapped.Players can't pay life to cast spells or to activate abilities that aren't mana abilities.{X}, {T}, Exile Karn's Sylex: Destroy each nonland permanent with mana value X or less. Activate only as a sorcery.