Each victorious brawl will give you a card pack to unlock. You can have a total of three card packs at the time. You can unlock one card pack at a time, which will take a minimum of 3 hours. 

In order to unlock the Chief Pack, you need 5 victorious brawls. Once redeemed, the next available Chief Pack will unlock after a certain amount of time and again need 5 victories to open.