CARD STAR UPGRADE RULES
To upgrade a card, you need to consume a certain number of cards of the same star level and a certain number of advanced gems. For example: SR: 4-star to 5-star: 2 identical 4-star hero cards,54-star hero cards of the same race, 4 3-star hero cards of the same race
LEVEL ADVANCEMENT REQUIRED
Different levels require different gold coins and a certain number of advancement stones. After the level is advanced, you can unlock the relevant level skills and obtain the improvement of all the attributes of the hero.