Citanul Flute

Tutoring for creatures, scaled to a dial you control. The X in the activation is the entire design: pay nothing and you fetch a creature with mana value zero or less, pay a fortune and you reach for anything in your deck. That sliding cost is what holds the rate in check. It does not bury anything, it does not cheat mana values, and it puts the creature in your hand rather than onto the battlefield, so the cast still has to happen on its own terms. What pushes it so high is the colorlessness: any deck running creatures can run this, and the artifact slot means a five-color toolbox can lean on it without a single colored pip. The flute rewards a deck full of singleton bullets, the one big finisher and the one situational answer and the one combo piece, because the same activation reaches all of them at whatever cost the board demands. It is slow by modern standards (you are sinking a whole turn's mana into a single card every time you tap it), but that slowness buys the flexibility, and the flexibility is total. The colorless creature tutor has been redesigned many times since, often with restrictions on what it can find or how it delivers the card; this version simply asks for mana and hands you exactly the creature you need.