Frilled Cave-Wurm

The 2/5 body is a wall by default, a defensive blue creature built to trade toughness for time. The descend clause reframes what that body is for: fill the graveyard with four permanent cards and it swings to 4/5, a stat line that suddenly attacks into most early boards without dying to the same-size blocker it used to invite. The design is honest about the tradeoff. Blue does not usually get to spend the early game accumulating a graveyard while also holding the ground, so the threshold pays out only once your engine has already been humming, and until then you own a fair defensive creature and nothing more. What makes it a coherent common is that the reward matches the shell it lives in: a self-mill or sacrifice-adjacent deck already wants permanents piling up in the graveyard for other reasons, so the +2/+0 comes along as a free byproduct of what the deck was doing anyway. The choice of four permanent cards (not any cards, not instants and sorceries) narrows the counting to the exact resource those decks generate, keeping the buff from flipping on accidentally in an unrelated shell. It is a role-player, a common-slot body that starts as a blocker and graduates into a clock once the graveyard does its work.