Occasionally you might receive some Wildcards when opening Card Packs. These cards can be exchanged for any other card in a collection that you don't already own. Please note, the color/rarity of the wildcard needs to match the card that you want to unlock.

The card colors correspond to their rarity:

Green - Common
Blue - Rare
Purple - Epic
Yellow - Legendary

Simply go into the Album with the card you want to reveal, tap on it, and you will have the option of using your Wildcards to unlock it!