Last March of the Ents

More explosive than Improvisation Capstone, but its eight-mana, board-dependent setup is a poor fit outside mana-heavy creature shells.

Could be wrong if UrzaTron may have enough mana and large creatures to make a one-of payoff materially better than expected.

It is stronger than Improvisation Capstone when set up, but eight mana, double green, and requiring a creature already in play are severe costs.

Could be wrong if Fast-mana creature-combo shells could make the uncounterable mass deployment more practical than it appears.

A large creature can turn this into a major refill plus mass deployment, but eight mana and needing both board and hand make it specialized.

Could be wrong if Creature-ramp decks may reliably cast it with enough toughness and hand size for it to become a stronger finisher.

With any substantial creature in play, it can draw several cards and deploy a full hand; the eight-mana cost and setup keep it below bomb status.

Could be wrong if Unknown format speed, removal, and creature sizing determine how often its expensive setup is achievable.