A new that adding a new adventure mode was a case of correct timing.

"Our goal going forwards is to figure out the right pace of adding in more expansions and adventures," he said.

"We have to time it so that players are ready for a new batch of cards. We're not going to go in too fast either."

The third card back, called the "Golden Celebration", is likely to be a reward marking the one-year anniversary of the game. Hearthstone officially launched on March 11 last year.