Gems are the game's premium currency. They are spent to get the best cards from the Card Shop (Gem Draw) as well as to improve your heroes. Gems are occasionally given as a reward instead of cards for logging in daily in the game. Complete the daily challenges to earn gems. Participate in Arena battles. You will earn five gems each time you start a new battle in the Arena, regardless of outcome. You will also get gems if you record and share your battle replay. When you advance to a new Arena rank, you will be given gems.