Fungusaur

Damage as a resource, written down for the first time. The trigger converts any damage the creature survives into permanence, which inverts the usual combat math: a blocker that lives through a strike walks away bigger than it started. There is a hard wall the creature cannot clear, though. The counter goes on only if it is still on the battlefield when the trigger resolves, so lethal damage kills it outright before the ability ever resolves: a 2/2 that eats three from any source is just dead. The growth only compounds when the damage falls short of toughness, which means the engine asks for chip damage, surplus combat strikes, and pingers that tap for one, not a clean removal spell. A 2/2 for four mana is steep by modern rates, and that is the toll for a keyword-free upside: the stat line wants to be attacked into rather than with. What the card prototyped is the lineage green and red have revisited for decades: the creature that grows from being struck and survives, the design axis later formalized as Enrage on cards like Ripjaw Raptor, and echoed in damage-into-counters builds like Phytohydra. The mechanic now reads as a stock design lever; this is where it was first sketched, before the +1/+1 counter was the color's default currency.