Gust of Wind

Two mana bounces a nonland permanent and replaces itself with a card; four mana does the same, and only one of those prices is worth casting. The cost reduction hinges on controlling any creature with flying, and that condition rewrites the spell entirely: at full price it is an overcosted bounce-cantrip nobody builds around, but tie the discount to a battlefield state a flyers-and-tempo deck already occupies and the removal folds into the board you were committing to the air anyway, with a fresh card to keep the pressure on. Note what the reduction does and does not care about: any flyer unlocks it, so the enabler is broad rather than tribal, and the discount is a flat floor, not a scaling engine that keeps getting cheaper. There is also a quiet asymmetry worth naming. It targets a permanent you do not control, so it cannot save your own creature from removal or reset your own enters-the-battlefield trigger. It is aimed outward, at their board, which keeps the tempo swing pointed the right direction and stops it from doubling as a self-targeting combo piece. The whole card is a bet that a discount you have to earn is more interesting than a rate handed to you flat: pay the deckbuilding cost of committing to the air, and a mediocre bounce spell becomes a genuine tempo play.