Ornery Tumblewagg

Counter accrual usually scales linearly: one per combat, one per proliferate, a slow climb that removal interrupts before it matters. This Brushwagg breaks that curve by multiplying instead of adding. The combat trigger drops a +1/+1 counter on a creature at the start of each of your combats, which is a modest boost on its own; the real payoff is the attack trigger, which doubles the counters on a target creature whenever this thing swings while saddled. Two counters become four, four become eight, and a board that looked survivable last turn is suddenly lethal. The doubling is what turns a grind into a kill.

The design manages that power with the saddle gate: the doubling fires only when the Mount is saddled, and saddling demands a real commitment, tapping other creatures with total power 2 or more before combat can begin. You cannot flash the Mount in and immediately geometric-growth someone; you have to build a board first, then survive to the combat step where the numbers explode. Because the trigger targets any creature, the doubling can be aimed wherever it hurts most, not just at the saddled creature or the Brushwagg itself, so the counters pile onto whichever threat is hardest to answer. Exponential counter growth has surfaced before in green as a reward for setup; folding it into the Mount and Saddle framework gives it a repeatable body, a clear price of admission, and a target that keeps shifting to the least answerable creature on the board.