You can enhance your cards by sacrificing unneeded cards to upgrade a base card. The improved cards will gain new abilities as they reach certain levels. Some of them will gain abilities that are related to their class.
Deck building
Protector cards have high health but deal low amounts of damage. They have "Taunt" abilities, which force all currently played opponent cards on the board to attack the Protector card, no matter where they are placed. Use Protector cards to prepare large damage combos or protect your Priest cards. Try to have always have one Protector card in your deck. Also have at least one Priest, as well as one Enchanter to buff your team. The remaining positions should be Mage or Assassin cards, which are the main source of damage.
General strategy
Your opponent can be defeated by either destroyubg all of their cards or bringing their HP to zero. If your opponent engages directly with you, cover your weak spots while attacking their openings. If they are whittling down your cards slowly, do your best to take them out.
Gold
The online reward can be collected every ten minutes, then a gradual increase of five minutes each time it is collected. Tap the chest icon at the top left corner to collect. Each time it is collected, you will receive 10,000 gold and 10 gems.
Hero abilities
Each hero has a unique ability that can be used during your turn. However, each ability has a limited number of charges. Only use them at the proper moment.