If the target creature is an illegal target when Fists of Ironwood tries to resolve, Fists of Ironwood won't resolve and won't enter the battlefield
This was clearly a test of the concept of serialized cards in Magic, but to my knowledge, their existence has never been officially acknowledged by anyone at Wizards
A bundle of Magic
Its ability to turn lands into useful spells in an ongoing way is difficult to disrupt and really hard to beat for any slower deck, even a deck that simply requires a certain mass of hand size to go off
Although the early days of Disney Lorcana were plagued by stock issues, recent expansions have been more stable, so it shouldn't be difficult to pick up Shimmering Skies
Per the industry trade ICv2 : ...the number of unique players attending Commander events per week at WPN stores went from 9,000 in 2018 to 28,000 in 2020