Arboretum Elemental

Convoke is doing something quietly aggressive here that it rarely gets to do: it is collapsing a nine-mana spell into something a wide green board can deploy on turn four or five. The printed cost of is sticker price, not real cost. Tap a handful of creatures (each one paying or a green pip) and the 7/5 lands far ahead of schedule, which is the entire reason the body skews so far toward power. The hexproof is the second half of the bargain. Most untargetable threats in green are smaller, cheaper, and built to carry an aura; this one is built to survive the spot removal that punishes a tapped-out convoke turn. You empty your hand and your board into one creature, and the reward is that the one creature cannot be answered by a single targeted spell. That is the tension the design resolves: convoke leaves you exposed the turn you go off, and hexproof on a large body is the insurance that keeps the play from being a trap. The limitation, such as it is, lives in the convoke math itself. The cheaper you cast it, the fewer untapped blockers you keep, so a turn that resolves an unkillable 7/5 can also be the turn you have nothing back. It is a finisher that asks you to win quickly with what survives, not a value engine you grind behind.