Dromoka Captain

Bolster resolves without a target: it looks for whichever of your creatures has the least toughness and puts a +1/+1 counter there. When the board is tied for that low point, you pick among the frailest, but there is never anything to aim at, which is the structural thing that matters here. As a 1/1 with first strike attacking into an early board, the Captain is usually the smallest body it controls, so the first counter lands on itself, pushing it to a 2/2 that trades up against two-toughness blockers and survives thanks to striking first. Swing alone and it keeps feeding itself. Add company and the character of the engine shifts: if the rest of your line is smaller or equal, the counters chase whatever is currently lowest, thickening the back of the board rather than piling onto one threat. Because the effect always follows the least-toughness creature and never picks a specific one, spot removal answers a body but not the plan: kill your biggest thing and the next attack simply pads whatever is left, and shroud or hexproof cannot deflect a counter that was never aimed. The decision the card poses is not per-turn but structural, shaping the board so bolster deposits its counters where you want them. Standing still, it contributes nothing; every point of value lives in the attack trigger compounding, so a board that cannot profitably swing switches the whole engine off.