Hi. You must use Credits to buy Quest Potions. It works out a lot cheaper than DEC. You can buy credits using PayPal or linking a crypto wallet (use the desktop app on a computer / Mac)
Once you a buy a Quest Potion it will automatically be used on your next daily quest. I buy 10 at a time for $7.50 worth if Credits, plus 1 extra bonus Potion is given for free. This gives me 55 extra Chests over 11 days.
11 Quest potions x 5 = 55 Chests!
One Gold card pays for the $7.50 I put in!