Voracious Hydra

The choice at the center of this card is where the tension lives: X pumps the body, and then the enter trigger asks whether you want that investment doubled or spent. Point it at an empty board and you get a genuine threat, a trampling creature that arrives at twice the counters you paid for. Point it at a blocker and you convert the same investment into removal, fighting a creature you don't control while your side keeps its full counter total to absorb the damage. That second mode is the interesting one, because the counters make the fight lopsided: the Hydra hits with its buffed power and survives with toughness to spare, so it functions as green removal that leaves a body behind rather than a one-for-one trade. The 0/1 printed base is a reminder that none of this happens for free; with X at zero the card is inert, and every point of size is mana you chose to spend before the mode ever resolves. What makes it durable across formats is that it never asks you to guess. You cast it knowing the board, and the modal choice resolves the same turn, so the flexibility is real rather than theoretical: a mana sink that is a threat when you need pressure and a fight spell when you need an answer, with the counters doing double duty as both the payment and the reward.