Ethereal Usher

Transmute always asks two things of a card at once: that it be worth running and that you be glad to throw it away, and this Spirit splits the difference by pairing a flimsy 2/3 body with an evasion ability that earns its keep only when you have something worth pushing through unblocked. The combat half is forgettable on its own, the kind of tap-to-enable trick that drifts into combo-finisher duty in a deck built to swing a single threat. The cargo is the transmute clause, which discards the card to fetch any six-mana spell from your library. That alignment is the whole constraint: transmute pulls only cards sharing this card's mana value, so its reach is bound entirely to whatever six-drops the deck wants to find. Run it alongside a fat finisher or a splashy top-end payoff and you get a flexible toolbox slot that never sits dead in your opening hand, since when you have no use for the unblockable line you cash it in for the threat you actually need. The searcher stays fixed while the payload shifts with every printing of six-mana payoffs, which is exactly the design space transmute was built to occupy: a creature priced as a creature, a tutor priced as a tutor, and a single card that lets you decide which one you needed after you've drawn it.