Dramatic Reversal

On its own, this untaps your board for two mana and accomplishes nothing: a tempo-neutral refresh of vigilance that any honest evaluation would file under "do not play." The card exists for the combo player, and specifically for the one piece of the puzzle that turns the untap into a loop. Crucially, it untaps nonland permanents only, so the engine has to live in your mana rocks rather than your lands. Pair it with rocks producing three or more mana between them (Isochron Scepter is the canonical partner, imprinting Dramatic Reversal so the untap can be recast at will), and "untap everything" becomes a closed system generating arbitrary mana every cycle. The self-reference is the whole design: a spell whose effect refreshes the very permanents that pay for its recast, given a board that produces more than the spell costs. It is the rare combo enabler that reads as pure filler until the second card arrives, at which point it stops being a spell you cast and becomes a button you hold down. The instant-speed clause matters too: the loop can fire in response to a removal attempt or while an opponent's turn is passing rather than committing on your own turn, so the engine assembles at the cleanest possible moment instead of telegraphing the kill a turn early.