Goreclaw, Terror of Qal Sisma

A flat off any creature spell with power 4 or greater is the whole engine, and the reason it warps a green deck's turns is not that the discount grows but that green's threats are already expensive enough for a fixed to matter enormously. A six-drop fatty and a five-drop beater both drop by the same two mana, but that two mana is precisely the difference between casting one oversized body a turn and chaining two or three, so a ramp deck stops needing to ramp and starts needing to only find fuel. The trigger keys off raw power rather than creature count or spell type, which pushes deckbuilding toward going tall: fewer, bigger monsters, each one clearing the power-four bar so the discount and the anthem both fire. That attack trigger is the closer, not the engine, since a board of huge creatures all gaining trample at once turns green's oldest problem (getting the giants through a clogged ground) into lethal in a single swing. Built as a 4/3 rather than something armored, it asks to be the thing pushing damage, not the thing surviving it, and a payload-discounter that dies to most burn is the restraint that keeps four mana of enabler in check. The card sits in a clear green lineage of "make your overcosted monsters castable on curve," sharpened here to reward being as top-heavy as the deck can stand.