Siege Wurm

Convoke turns a wide board into mana the way few other mechanics do, and a 5/5 trampler is exactly the payoff that idea was built to enable. The printed cost reads expensive, but the spell rarely costs full price: tap a few bodies sideways before combat (or after) and the seven mana collapses to whatever your green creatures can shave off, often landing the wurm several turns ahead of schedule. The catch is the one convoke always negotiates: a token-and-creature deck wants to swing with those bodies, not tap them to cast spells, so casting this forces a choice about which turn the board is better spent as a beater and which turn it is better spent as fuel. Trample is what makes the conversion pay off: a creature you ramped out with smaller creatures should not get chump-blocked into irrelevance, so the keyword guarantees the damage punches through whatever blockers your opponent has left. It is clean, honest green go-wide design, a curve-topper that rewards a board already broad enough to need a finisher and gives that board somewhere to spend itself.