Ezuri, Stalker of Spheres

Every prior Ezuri leaned on one number: Ezuri, Renegade Leader tapped elves into an overrun, Ezuri, Claw of Progress banked experience counters off small attackers. This one turns proliferate itself into the engine, and that is the whole shift. The second ability fires on every proliferate event, not just its own, so it converts a mechanic that normally does incremental board work into a repeatable card-draw trigger. The entering ability is the down payment: pay the optional cost and you proliferate twice, which reads as two immediate cards plus whatever counters you happen to be nursing. But the design's real reach is that Ezuri does not care where the proliferate comes from. Any external proliferate, a planeswalker's loyalty ability, a resolving spell, another creature's trigger, feeds the draw, so the card scales with a whole family of effects rather than a single counter total. That is what makes it a build-around rather than a value creature: the body is a fragile 3/3, and the payoff only materializes in a deck stuffed with counters worth multiplying and the sources to multiply them. It sits at the intersection of the two axes green-blue has always wanted to marry, +1/+1 counter accumulation and card advantage, and resolves them into a single engine piece. The tension is fragility against ceiling: cheap to kill, but left alone for a turn cycle it draws deep enough to bury an unprepared opponent.