再鍛されたレガシー、カーン

再鍛されたレガシー、カーンのパワーとタフネスはそれぞれ、あなたがコントロールしているアーティファクトのマナ総量の中の最大値に等しい。
あなたのアップキープの開始時に、あなたがコントロールしているアーティファクト１つにつき{C}を加える。このマナはアーティファクトでない呪文を唱えるためには支払えない。ターン終了時まで、ステップやフェイズの終了に際してあなたはこのマナを失わない。

神兵重铸卡恩

神兵重铸卡恩的力量和防御力各等同于由你操控之神器中的最大法术力值。
在你的维持开始时，你每操控一个神器，便加{C}。此法术力不能用来施放非神器咒语。直到回合结束，你不会因步骤与阶段结束失去这份法术力。

Karn, Legacy Reforged

Karn, Legacy Reforged's power and toughness are each equal to the greatest mana value among artifacts you control.
At the beginning of your upkeep, add {C} for each artifact you control. This mana can't be spent to cast nonartifact spells. Until end of turn, you don't lose this mana as steps and phases end.

Mystery Booster 2

March of the Machine: The Aftermath

Karn's last ability isn't a mana ability, even though it adds mana. It uses the stack and it can be responded to. Use the number of artifacts you control as the ability resolves to determine how much mana to add.

The ability that defines Karn's power and toughness works in all zones, not just the battlefield. As long as Karn is under your control and still an artifact, its own mana value will count. In most cases, it'll be at least 5/5.

The mana produced by Karn's last ability can be spent on anything that isn't a nonartifact spell. This includes casting artifact spells, paying costs to activate abilities of both artifact and nonartifact permanents, paying ward costs, and so on.