In MTG Arena, a wildcard is a card that can be traded for another card of the same rarity. Wildcards can be obtained in booster packs, and are available in all rarities: common, uncommon, rare, and mythic rare. As you acquire commons and uncommons of which you already own 4 copies, you earn progress to fill your Vault. Once you fill your Vault, you also get wildcards - 3 uncommon, 2 rare, and 1 mythic.
There are a few ways to turn a wildcard into a card you'd like:
- If you already have a copy of the card, you can just click it in your collection without first clicking the Wildcard button.
- If you don't have a copy of the card, change the filters to include Not Collected cards, search for the card, then click it.
- While editing a deck, if you attempt to add more copies of a card than you own to a deck, you'll be prompted to redeem a wildcard for that card.
- If you import a deck containing cards you don't own, there's a Craft All button by the Done button in deck edit you can use to craft all the missing cards.
You can mouse over the wildcard icon in the top of the client to see how many wildcards of each rarity you have currently.