Invigorating Surge

The math is the whole point: put a counter on, then double, so the card always adds one before it multiplies. On an empty creature that means two counters for three mana, a rate nobody blinks at. On a creature already carrying four, it means putting one and jumping to ten, and the returns only steepen from there. This is the classic doubler trap, the reason effects that multiply counters rather than add them are priced so carefully: their floor is dull and their ceiling is a game-ending swing that arrives at instant speed. The window that makes it worth the slot is combat. Held up until an attacker is committed and unblocked (or blocked by something too small to matter), it converts a creature that was already scaling into a lethal one after the opponent's blocking decisions are already made. It rewards decks that have already invested in counters, and it does nothing to bail out a board that has not; the effect is a payoff, not an engine. Green has a long line of counter-doublers doing structurally similar work, but most attach to a permanent or a static ability. Packaging the double onto a cheap instant is what gives this one its teeth: no telegraphing, no board presence for the opponent to answer in advance, just a trick that turns a good attack into an unanswerable one.