Serum Snare

Bounce with a rider tied to the size of what it hits. The base effect is generic tempo: return any nonland permanent to hand at instant speed, no better a rate than the templates it descends from. The proliferate clause is what earns the ink, and it fires only when the target was cheap enough to qualify. Read as a straight aggro reward, that condition looks minor. Read against a board that already has counters on it, it changes the card's axis: bounce a small creature, then advance every planeswalker's loyalty, every charge counter, every poison marker, every +1/+1 you control. The design welds two effects that usually live in separate decks, the interaction of a bounce spell and the payoff of a counter-matters engine, and it makes you clear the same bar to collect both halves at once. Against an expensive threat you get clean tempo and nothing else. Against the small creatures aggressive and combo shells lean on, you get tempo plus an incremental push on whatever counter plan you are running. It wants counters on the battlefield the instant the spell resolves, which is a narrower demand than plain bounce but a more rewarding one when the pieces are already there.