Impervious Greatwurm

The largest creature ever stamped with a printed power and toughness, and the number is the whole pitch: a 16/16 is not a body you cast for value, it is a body you cast to end the conversation. Convoke is what lets the size land sooner than ten mana ever should: a battlefield of green creatures can tap to discount the cost dramatically, so a wide board converts into a single indestructible threat that no longer cares about the small attackers that paid for it. That conversion is the design tension. The card wants you to commit a board first, then trade that board's width for a body so large that most of what a green deck fears (burn that can't scale, fight effects that can't out-toughness it, damage-based sweepers) simply washes off. Indestructible handles the symmetric wraths and the destroy-target-creature spells too, which is what separates a finisher from a mere fatty. What it does not answer is telling: bounce still sends it back to hand, exile removes it cleanly, and edicts or shrink effects go around the keyword entirely. There is no trample, no haste, no evasion stapled on, and that restraint is deliberate: the card's only job is to be too big to kill by damage and too big to ignore, leaving the question of how to actually connect to the deck built around it.