Evolving Adaptive

A one-drop that starts as a 1/1 (the oil counter it enters with does the counting), then grows every time you play something bigger than it currently is. The trigger is the clever part: it does not care about creature type or color or keyword, only that the new arrival outclasses the current body in power or toughness. That builds a natural growth curve into an aggressive green sequence, since each escalating threat you cast quietly feeds the smallest creature on the board rather than leaving it behind. The catch is self-limiting: once this thing has stacked enough counters to become large, it stops being easy to trigger, because now your new creatures have to beat its inflated size to matter. So the reward tapers exactly as the payoff peaks, which is what keeps a free-scaling one-drop from running away. It rewards playing on curve into progressively bigger creatures, not going wide with copies of the same body. The oil-counter framing ties it to the proliferate designs that share the mechanic: any effect that adds counters outside the trigger sidesteps the "must be bigger" clause entirely, letting the body swell without needing a parade of larger creatures to enable it.