Woodwraith Corrupter

Most Golgari top-end is a fat attacker that trades down to a single removal spell; this 3/6 inverts that arithmetic. The wall holds the ground while the army grows out of the manabase behind it. Tap it and a Forest becomes a 4/4 black and green Elemental Horror with no duration attached: the body sticks around, still a land, and a fresh one accrues every turn you have a Forest to point at. That permanence is what makes it a grinder. As long as the 3/6 survives and Forests remain to feed, you manufacture a 4/4 a turn, hiding each new threat in your land base instead of committing fragile creatures from hand. The target is any Forest, not just yours, but the ability does not steal: animate an opponent's Forest and it becomes a creature its controller still owns and can swing back at you with, so the only sensible line is feeding your own lands. Land animation as a one-card army has deep green roots (Kamahl, Fist of Krosa swings the whole board at once; Living Lands flips everything in a single cast), but those are explosive and symmetrical where this is patient and one-sided: repeatable, paid out a single activation at a time, telegraphing nothing until a Forest stands up and attacks. The triple-pip cost across two colors makes it a payoff a Forest-heavy deck builds toward, a win condition that survives removal by refusing to announce itself.