Urdnan, Dromoka Warrior

The counter placed on entry is a down payment, not just a stat boost: it is the fuel for a second, escalating payoff that only reads during your own attack step. Whenever you swing, an attacking creature with a single counter gains first strike, and one carrying two or more upgrades to double strike, so the same resource that grows a body also decides how hard it hits when it turns sideways. That two-tier attack trigger is the whole engine. One counter turns a modest attacker into a first striker that trades up in combat; stack a second and the swing becomes lopsided, since double strike doubles the counter-inflated damage and any other combat modifier riding along. The reward curve is steep enough that this wants a counters-focused shell, where the enter trigger primes a target and the attack trigger cashes it in every turn you swing. Costing only two and swinging a mere 1/1, it comes down early to start the accumulation before the board even matters. Where most counter-matters designs reward going wide or grinding out incremental value, this one rewards going tall on a single threat and then attacking with it, converting vertical growth directly into lethal math. The elegance is that both triggers reference the same counters from opposite ends: one puts them down, the other reads them back out as combat keywords, but only on the turns you commit to the offense.