Regarding the legality of the cards: Magic: The GatheringFINAL FANTASY (FIN) is a Standard-legal set Magic: The GatheringFINAL FANTASY Commander (FIC) and FINAL FANTASY Through the Ages (FCA) are Commander-, Legacy-, and Vintage-legal sets, and individual cards are also legal where already available in other formats Magic: The Gathering FINAL FANTASY Play Boosters contain cards from FIN and FCA
It's the best rule that we have
until the End Phase, this card's name becomes that monster's original name, and replace this effect with that monster's original effects, also for the rest of this turn, if your monster attacks a Defense Position monster, inflict piercing battle damage to your opponent
If all targets are illegal when the spell tries to resolve, the spell doesn't resolve and none of its effects happen
Luffy, Manga Alternate Art Secret Rare, OP-05 119 ($1,700) Its almost certainly not a surprise to see a card featuring Monkey D
Machamp can be obtained from Fantastical Parade pack in the Fantastical Parade set