Wildcall

Manifest's central appeal is that it sells you a mystery: you get a 2/2 with a possible spell tucked underneath, and the manifest mechanic itself was a refinement of morph, a way to put any top-of-library card onto the battlefield face down rather than only the morph-enabled creatures of an earlier era. What this spell adds to that template is scale. The X in the cost feeds counters onto whatever lands face down, so the same instinct that builds a green ramp engine can pour mana into a body of arbitrary size with a card hidden under it. The trick is that the manifested permanent is a creature regardless of what it actually is: a noncreature card sits there as a counter-pumped 2/2-grown vanilla beater, unable to flip, while a creature card can be turned face up later for its mana cost with all those counters intact. That asymmetry is the deckbuilding question the card poses. Run it in a deck full of fatties and you are effectively cheating a large creature into play with a free downpayment of stats; run it with a fat noncreature top, and you have spent your green on a blank growth spell. The counters being on the permanent rather than the spell also means flipping does not reset them, so a beefed-up manifest that reveals a real creature keeps every point you paid for.