Because this set was the first to do so, many of these cards are valuable
The most obvious answer beyond that was seeing what rare or mythic rare you opened, or if you found that key uncommon or common for your deck
Final Fantasy Through the Ages: Yawgmoth, Thran Physician (0011 - The Emperor, Hell Tyrant) NM EX VG G Other Versions Customers who purchased Final Fantasy Through the Ages : Yawgmoth, Thran Physician (0011 - The Emperor, Hell Tyrant) also bought
Let's take a look at two Supporters real quick, Maxie's Hidden Ball Trick from XY Primal Clash and Lysandre's Trump card from XY Phantom Forces
While this challenge will take a while to complete, let's just be happy we don't have to collect over 900 cards to complete it
Be sure to share your decks and favorite cards in the comments