Corpsejack Menace

Doubling is a mechanic that scales nonlinearly, and this Fungus turns that math into a body. The replacement effect rewrites every counter event you control: a single +1/+1 counter becomes two, a graft trigger becomes a windfall, a proliferate's added counter is doubled. The structural choice that matters is the word "would," which makes this a replacement effect rather than a triggered one. It intercepts the counters before they land rather than reacting after the fact, so anything that puts +1/+1 counters on your creatures (combat pumps, modular, evolve, outlast, hardened-scale accumulation) gets multiplied at the source. The boundaries of the ability are precise, and worth respecting: it touches +1/+1 counters on creatures you control and nothing else, so loyalty on a planeswalker and the -1/-1 counters of infect or wither sit entirely outside its reach. The cost of all that exponential ceiling is that it does nothing for you until something else moves first; the card is a multiplier with no input of its own, a 4/4 that has to wait for a partner to justify its slot. That dependency is the price the design pays for an ability that can otherwise spiral games out of reach. Two copies compound into quadrupling, which is the kind of interaction counter-themed decks have chased since they first had a payoff to build toward: an effect that asks you to generate counters, then pays you back on a curve the opponent cannot match.