The term "defending player" in the myriad rules (or any other ability of an attacking creature) refers to the player the creature with myriad was attacking at the time it became an attacking creature this combat, the controller of the planeswalker the creature was attacking at the time it became an attacking creature this combat, or the protector of the battle this creature was attacking at the time it became an attacking creature this combat
This perhaps points to the fact that the more balanced and flexible Emerald Ink pairs well with the magic and enchantments of Amethyst
Another interesting choice WotC made is to introduce some Final Fantasy characters as in-universe Magic: The Gathering cards
With that in mind, Nuclear Fallout can function as both a board wipe and a win condition
For example, Adrix and Nev, Twincasters and Esix, Fractal Bloom could power out an army of hard-to-deal-with tokens that will only get bigger
That and its near one hundred dollar price tag