Iona is a 7/7 Legendary Creature with Flying, and when she enters the battlefield, you choose a color, preventing your opponents from casting any permanent spells of that color
No other Magic creature can populate the board as efficiently and early as the Sergeant
Weve covered the Organized Play stuff in another article
As mentioned above, you could try combining them with Emry, since Emry makes it advantageous to end up with artifacts in your graveyard and Crystals let you do that more reliably
The front side is most valuable in mono-colored or colorless decks that struggle with removal, while the backside likes multicolored cards, specifically two-color cards
Madam Mim, Rival of Merlin A wickedly powerful witch Making her first of several appearances among the best amethyst cards in Rise of the Floodborn is Madam Mim, here in her human form as Madam Mim, Rival of Merlin