I tried this out for Foundations and found that the following 12 cards are part of the set but not in boosters: (gameaper) set:fdn -in:boosterWe should turn this thread into "favorite scryfall hacks" real quick so I can learn some stuff. I'll start.
When I'm midgame on Arena I use "in:booster" to make sure I'm playing around combat tricks that are actually in the set.
Why aren't those cards in boosters? What's going on?