Some Card packs that you receive contain duplicate cards. These are cards you have already collected, and they don't bring you any closer to completing a set. But duplicates can still help you!

- Gather duplicate cards to open reward chests
As you accumulate duplicates, the number of stars from duplicate cards increases. Collect more stars to open reward chests. Duplicates of 5-star Gold cards are especially valuable: they give you 10 stars for opening chests.