Hungering Hydra

Most X-cost hydras price their bodies and walk into combat as a stat-stick: you pay for the counters once and hope the math holds. The wrinkle here is a feedback loop wired directly into the combat step. Because it survives-then-grows, any damage that fails to kill it is converted into permanent size, which inverts the usual logic of trading or chump-blocking. Block it with a 3/3 and the 3/3 dies while the Hydra walks away three counters fatter; throw a burn spell short of lethal at it and you have just fed it. The "can't be blocked by more than one creature" clause is what makes this threatening rather than a curiosity: it forces opponents to either find a single blocker large enough to kill it outright (eating the growth if they miss) or let it through and absorb the damage, and it shrugs off gang-blocks that would normally pin a lone attacker. The result is a creature that punishes imprecise removal and imprecise blocking equally, where the opponent's correct line is almost always "kill it cleanly or don't touch it." That binary is the whole point: it turns the everyday decisions of combat and removal math into a trap, and a green deck's job is simply to keep handing the opponent worse and worse versions of that choice.