The currency used to create or craft new cards is inks and it is obtained by disenchanting excess cards. Disenchanting cards is performed in one exchange at the 'Crafting' menu where the game will automatically take all duplicate cards possessed in excess of their limit and exchange those extra copies for inks. The number of inks you will recieve in return is determined by the card quantity and rarity. The card rarity, number of inks received in return per card rarity value, plus the total amount of inks credited to the player will be displayed.