Zar Ojanen, Scion of Efrava

The trigger key is the one design choice that separates this from the usual counter-payoff commanders: the counters land when it becomes tapped, not when it attacks. That distinction is doing real work, and it points the build away from the obvious. A creature tapping to attack is the mundane case, but tapping to crew a Vehicle, to convoke a spell, or to pay for an activated ability all fire the same anthem, which means the payoff wants a shell that treats tapping as a resource rather than only a combat step. Note the anti-synergy this creates: giving it vigilance would let it attack without tapping, suppressing the very trigger you want during combat. The Domain gate is the second lever, and it scales the effect two ways at once: a wider set of basic land types raises the toughness threshold, so more of your board qualifies, while each counter reaches the small creatures you most want to grow. One basic type is a narrow, almost embarrassing trigger; five turns it into a board-wide pump for everything with toughness four or less. The distribution rewards going wide with small bodies over tall with a couple of fatties, since a lone giant already clears the bar and gets nothing. And the 4/4 frame sits exactly on the fault line: at four basic types it excludes itself, but push to five and its own toughness of 4 falls under the threshold, so the last land type you find is also the one that finally lets it grow itself.