Old-Growth Educator

Infusion is a conditional buff gated behind sequencing: the two counters cost no mana, but they cost you a life-gain trigger somewhere earlier in the turn, checked once as the trigger resolves. That timing window is the whole design. A 4/4 with vigilance and reach at this cost is already a fair defensive body, the kind that trades up on the ground and walls a flier at once; the infusion clause makes it a 6/6 for the same investment whenever the rest of your turn has done its homework first. What sharpens the ability is that it checks life gained this turn, not lifelink stapled to the creature, so the payoff comes from a deck that has already bled value before the trigger resolves: a Soul Warden ping, a drain effect two turns deep, any incidental gain that has resolved. It asks Golgari to behave like a lifegain deck without a single point of lifelink attached, which is an unusual ask for the color pair. Reach and vigilance are the tell that this was built as a blocker first and a beater second: it wants to sit back, wall the air, and threaten a swing back the same turn. Because this is a one-time enter-the-battlefield check rather than an ongoing engine, the sequencing has to be right when it lands. But the counters are permanent once placed, so a single satisfied condition leaves a durable 6/6 rather than a buff that evaporates at end of turn.