Yew Spirit

Doubling power is a deceptively dangerous wording, because the bonus reads off the already-buffed number rather than the printed base. Starting from a 3/3, the first activation makes a 6/6, the second a 12/12, the third a 24/24, each for the same four mana. That compounding curve is the unusual reward structure where a hand clogged with lands turns into a kill clock instead of dead draws: the threat scales with mana available across a turn, not with mana sunk into any single use. What keeps it short of a true combo piece is the narrowness of the buff. It touches only this creature's own power, and only until end of turn, so the entire investment evaporates if the Spirit is removed in response or simply walls into something it cannot punch through. Green has long flirted with this self-referential scaling in its pump-the-fattie tradition, but most attempts lean on static buffs or one-shot tricks; folding the doubling into a repeatable activated ability turns an unremarkable body into a threat that demands an answer before combat math runs away. It wants an open board and a fistful of forests, then closes in a hurry once it has both.