It is hard to believe that a card battling game has become one of the most successful video games on the market today, but somehow Blizzard Entertainment’s Heathstone: Heroes of Warcraft has managed to reach over 30 million players and reportedly earns $155,000 a day.

“BY THE POWER OF RAGNAROS, 30 million players have joined us by the hearth! Thanks for pulling up a chair!” the game’s official Twitter account announced today.

Hearthstone was released a little over a year ago for Windows and OS X, and it received an iPad version a month later. While the game has been a success for the last year, interest in the title had cooled somewhat until Blizzard finally released the long awaited mobile version for iOS and Android devices.

While free-to-play games often have little difficulty achieving large numbers of players (who doesn’t like free stuff?), a fair amount of Hearthstone’s success can be attributed to the game’s popularity with the esports and livestreaming crowd.

For the month of March, Hearthstone was the fourth most-watched game on popular livestreaming site Twitch.tv, and there are frequent tournaments for the game with grand prizes as high as $250,000. Out of the many popular esports titles viewed on Twitch, Hearthstone the only exclusively 1 v 1 game in the top 20.

In February, Activision Blizzard specifically called out Hearthstone during its Q4 2014 earnings call as being one of the publisher’s top new releases for the year. The company is expected to release its Q1 2015 earnings today, and industry analyst Doug Creutz of Cowen & Company wrote to investors that Hearthstone continues to be a valuable asset to the publisher’s game portfolio.

“The game’s recent performance is being buoyed by the release of the Blackrock Mountain expansion pack, which began rolling out content in early April,” Creutz wrote, as reported by Gamespot. “Additionally, we do not know to what extent the smartphone spending is incremental to or cannibalizing the existing PC/tablet base. Still, we view the performance as a very positive indicator for the trajectory of the game.”

While Hearthstone is free-to-play, it earns money by selling card booster packs, which contain a random assortment of cards, and by charging a fee to unlock new expansion content.

Screenshot by Eric David