Wavesifter

The evoke cost splits the card into two entirely separate jobs, and the deck decides which at cast time. Pay full price and you get a flying 3/2 that leaves two Clues behind: a fair body attached to a card-advantage engine that draws its own two replacements over time. Cast it for and the body sacrifices itself on entry, leaving two Clue tokens for two mana. That second mode is the one designers were pricing carefully, because it turns this into a cheap, sacrificable artifact factory: instant fodder for anything that counts permanents entering, dies triggers, or artifacts to feed, delivered at a rate that stays honest only because the Clues still cost mana to crack. Investigating twice rather than once is what earns the evoke line, since a single Clue for would be filler; two Clues plus the option of a flier when you want the creature instead is what keeps the card relevant across radically different decks. Among evoke Elementals that treat their own body as an optional cost, most cash the creature for a spell-like effect that resolves and is gone. This one cashes it for permanents that stick around and reward being sacrificed later. That is the structural difference: one card, and the mode you choose changes not just its rate but the kind of deck it belongs to.