Drumbellower

Vigilance lets a creature stay untapped after attacking so it can still block; this Spirit sells something stranger, and it sells it to the whole table. By untapping your creatures during every other player's untap step, it hands you fresh blockers on rotations that were never yours, a form of pseudo-vigilance that scales with the number of opponents rather than with any single turn cycle. You cannot swing on those turns (attackers are declared only on your own combat), so the real currency is the tap cost itself: any creature whose ability requires tapping (mana dorks, tapper effects, creatures you crew or convoke with) gets to fire once per player's untap step rather than once per your own, and a many-player game multiplies those windows accordingly. The catch is that the 2/1 flying body holds none of this together; it is a fragile enabler that dies to almost anything, so the engine only pays off if it survives a lap of the table. It runs the same clock as Seedborn Muse, whose untapping also lands on other players' untap steps, but narrows the effect down to creatures alone and staples it to a color that rarely gets this kind of relentless loop. That narrowing is what keeps it from breaking: it never touches lands, so this is no mana-doubling engine. The value pools instead in creature-based tappers and repeatable tap abilities, which is exactly where white wants it.