If you have extra cards or cards you don't plan to use in your deck, you can Recycle them.
Recycling cards will grant you Dust, which can be used to upgrade other cards and enhance their strength. The amount of Dust you receive is based on the card's rarity.
To Recycle:
Menu: Choose "Upgrade Cards" from the Main Menu. To Recycle: In the Upgrade Menu, select "To Recycle." Select Cards: Pick the cards you want to recycle. You can select up to 100 cards at a time, and selected cards will be highlighted. Use the sort/search/filter options if needed. Complete Process: Once you're satisfied with your selection, hit "Recycle" to increase your Dust total. The recycled cards will be removed from your Library. NOTE:
If you select a card that is above Level 1 or of Diamond rarity or higher, you will receive a warning that the card will be permanently lost after recycling to avoid accidental losses. Selecting "Clear" will deselect all chosen cards. Your current Dust total is displayed in the corner of the Recycle Menu. Selecting "To Upgrade" will return you to the Upgrade Menu.