Accumulate Wisdom

Most Lesson cards are static payoffs waiting in the sideboard for a Learn effect to fetch them. This one still lives there (it carries the subtype, so it can be pulled into hand like any other Lesson), but it also cares about the Lessons that came before it, checking the graveyard for three or more of them the moment it resolves. That flips the subtype from a one-way import into an accruing resource. Below the threshold, it is a two-mana dig-three-take-one: honest card selection at instant speed, one card traded for improved quality and nothing more. Cross three Lessons in the yard and the same spell keeps all three cards it looked at, a straight three-for-one with no restriction on what you take. The threshold does the balancing work, and it asks a specific thing of the deckbuilder: not to hoard Lessons in hand, but to have already cast them, converting each earlier Learn into a debt this instant collects on later. Even at full value it is a refuel, not a swing; spending two mana to draw without touching the board costs tempo now for cards later, so the payoff has to be worth the pause. What that reward is depends entirely on how many Lessons preceded it, which makes this a synergy piece dressed as a cantrip, worth exactly as much as the graveyard behind it.