In this event, you receive 1 free package of cards every 24 hours with various rewards.
For the rewards, you have an album that you need to fill in with the hero's cards, and for each hero, you also receive a bonus with the coins.
After collecting all the characters, you receive a mega bonus.
Moreover, after every purchase, you receive a key that allows you to unlock additional cards and get more rewards for them. Just try it out!