Rona's other side is Rona, Tolarian Obliterator, a huge 5/5 creature with trample that heavily punishes the opponent for dealing damage to it
Even a tiny deviation, something easily missed by the naked eye, can push a card below the thresholds required for top grades
Four mana for a haste anthem is already decent - but add cost reduction and threat duplication
Theres also a creature with double strike and trample in the deck, if there needs to be a single card to point towards and say this right here is what pushes Integrity over the top. On the topic of a crappy Lightning Helix, context, context, context
Iago - Giant Spectral Parrot is a clever addition to any Amethyst deck
7 Griselbrand Griselbrand may not be the most ridiculous creature on its list, but this demons strength is measured in several different ways besides its raw power