Sauron, the Dark Lord
The design problem with putting the Dark Lord on a card is that Sauron is defined by absence: a will radiating through servants, not a body swinging in combat. This resolves that tension by making the opponent build his army for him. Every spell an opponent casts feeds Amass, so the Orc horde grows in proportion to how much they try to do, and Sauron's own board presence is a byproduct of interaction he never spent a card on. The Ward is genuinely punishing by choice of currency: not life or generic mana, but a legendary artifact or legendary creature, forcing whoever wants to answer him to sacrifice one of their own marquee permanents to do it. That tax hits legend-heavy and artifact-dense decks precisely where they hold their best pieces. The engine's payoff runs through the Ring rather than around it: an Army connecting tempts you, and the tempt itself lets you throw away a spent hand for four fresh cards, a wheel that scales with how empty you already are. That last piece is the real motor. A deck built around this wants to dump its hand aggressively, because the refill is not a nice-to-have but the reward loop, and the Orcs supplying the combat damage are creatures the opponent effectively paid for with their own spellcasting. It is a rare marquee legend whose power grows the more the opposition tries to answer it.
