4 Polymorph Not What It Seems Originally printed in Mirage, Magics ninth expansion from 1996, Polymorph became the archetype for a number of unique cards that let you swap your creatures out for something else, with little control as to what happens along the way
Opt is a combat trick with prowess dorks or zero mana when you want to keep mana up to represent counterspells and you really don't need much extra on a one mana cantrip for it to be nuts
She might be somewhat expensive, but getting to cast spells for life in Commander is dangerously good
With Expressive Iteration being in so many decks and reaching all 4 copies even in a format like Vintage, I hear a lot of players saying the card is too good in both Modern and Legacy, comparing it essentially to Treasure Cruise and Dig Through Time, which both formats have seen and banned
The flavor of the games is evident in decks led by Sephiroth, Planet's Heir and Cloud, Planet's Champion