Mirror-Sigil Sergeant

The genius of the design is that it asks for almost nothing while threatening everything. A single blue permanent (an off-color enchantment, a stray creature splashed in) flips the switch, and from that point each upkeep can double your board of 4/4 tramplers if you let it. The growth is exponential rather than additive: one becomes two, two become four, and because every copy carries the same trigger, the engine compounds on itself with no further investment. What balances it is the seam between the trigger and the payoff. The token only arrives at the start of your upkeep, which means the opponent gets a full turn cycle to answer the original before it ever multiplies, and the conditional clause means a single piece of blue disruption (or simply no blue permanent to begin with) shuts the whole thing off. The body and the trample are mono-white, but the snowball is gated behind owning something blue, an unusual move for a card with no blue mana in its cost: the engine spends nothing but the requirement that you commit a slot to the right color rather than cast anything at all. The flavor reads clean, a sergeant cloning himself into a battalion, but the real interest is structural: a copy-on-upkeep loop priced behind a presence rather than an activation, where the cost of admission is what you already control instead of what you can pay.