Some cards have exploded in price, being worth over 20 times more now than they were merely a few days before the unbanning
If a spell or ability says that it would "destroy" a creature enchanted with an Aura that has umbra armor, that spell or ability is what causes the Aura to be destroyed instead
The remaining promo cards are available at in-store promo events or in specific Detective Pikachu collections
You can usually mulligan to six to try and find a Flourishing Fox, since games where you have that critter on turn one can be very lopsided
You ramp energy faster than any other type, draw extra cards for free, and heal through damage that would cripple other teams
Compared to most other attempts at free designs in Magic history, the X-cost caveat is an absolute masterstroke, adding an important wrinkle for deck builders which still leads to usefulness both in fair decks and less fair ones