Sylvan Advocate
A two-drop with a growth clause timed to fire exactly when a midrange deck wants it to: reach your sixth land and the 2/3 becomes a 4/5, no longer a body that trades down but one that swings for four and stays back to block thanks to vigilance. The land-count condition is the clever part. It costs nothing in deckbuilding, demands no investment beyond lands you were already running, and quietly converts a fair early body into a real threat at the precise point in the game where drawing more lands usually starts to hurt. The +2/+2 also reaches land creatures, which turns it into a payoff for manlands: the same buff lands on whatever you animate, so a board of activated creature-lands becomes a credible clock instead of a lone attacker. What leashes the upside is the benchmark itself. Below six lands it is a 2/3 with vigilance, fine on defense but easy to trade with, so the four-power configuration is something you earn over several turns rather than something handed over on turn two. That makes it curve-filler that justifies its slot twice: a competent early blocker, then a four-power vigilant body backed by a buff that scales across your whole land-creature base, all without asking anything else in the list to bend around its condition.
