By playing the Bullseye Challenge you can earn limited bags that contain packs of cards and strings!
The prizes are defined according to your current League and highest unlocked Tour. So the higher your League, the more cards you'll receive. And your highest unlocked Tour will define which cards will be available for you.

There are 5 different prizes and each one is unlocked after you achieve a minimum score. You can only claim one prize per round; if you score enough points to unlock more than one prize, the higher value prize will be claimed first.
As an example, if you score enough points to unlock the first two prizes, you will claim the prize that contains more cards and strings first!

You’ll have a limited amount of chances to claim all prizes. Once a prize is claimed, it is not possible to claim it again.
If you run out of chances, you can purchase more attempts. However, unused attempts will be lost once all prizes have been claimed or once the event ends.