Jidoor, Aristocratic Capital // Overture

The Adventure structure here answers a problem specific to mill: a mill spell is a spent card the instant it resolves, dead weight if it comes back off the top later. Overture halves an opponent's library in a single stroke, then instead of hitting the graveyard it goes to exile with the Jidoor side waiting, a tapped blue source you can play on any subsequent turn. The card never fully rots; the slot converts from spell to land. What you pay for that permanence is real. Six mana for the mill effect keeps it out of the opening turns entirely, so casting the spell half is a late-game commitment, not an early tempo play. The choice that matters is which mode you spend it on: drop it as a tapped land when you need the mana and fixing, or hold for six and fire the Overture, banking the land for later. Since Overture mills half the library rounded down, it scales with how deep the opponent's deck still is, so its ceiling comes against a full library rather than a nearly-empty one; the land-first line simply forfeits the spell. The elegance is that mill and control want opposite things from a nonland slot (payoff versus lands that don't clog the draw), and folding both onto one card lets a deck defer that decision from deckbuilding to the moment of play.