Rot Shambler

The deal here is simple: every creature you sacrifice, chump, or trade away leaves a permanent mark on this body. That makes it a mono-green answer to a question black usually owns, since the "grows when your stuff dies" engine is most often built around death triggers in Golgari shells. Stripped of that color pairing, this is a green aristocrats payoff, a 1/1 that compounds through attrition rather than a single big swing. The counters are the key word, because they accumulate on the battlefield rather than translating into a one-time burst, but that permanence is also the catch: the moment the Fungus is bounced to hand or blinked to exile, it returns as a fresh 1/1 with every counter gone. Shrinking it does not help your opponent much, but moving it between zones resets the whole project, and so does killing it outright before the snowball gets large. What keeps it honest is the rate it starts at. A two-mana 1/1 invites the first removal spell your opponent draws, and the ability does nothing on an empty board, so you are asked to supply the fodder yourself: tokens, expendable early drops, anything you were happy to throw under a blocker. Pair it with a sacrifice outlet and the dying stops being a downside and becomes the plan, each loop fattening the Fungus as the aristocrats machine spins around it. Filler in a vacuum, finisher in the right shell, with little in between.