Hearthstone: Heroes of Warcraft has surpassed 50 million registered players worldwide, Blizzard has announced.

The news comes as Whispers of the Old God, the game's third expansion, launches in Europe, bringing 134 new cards to the game.

"Whispers of the Old Gods adds an exciting new set of creepy, corrupted cards to Hearthstone," said Mike Morhaime, CEO and co-founder of Blizzard Entertainment. "We can't wait to see how creative players are with the ancient evil of the Old Gods in their hands."

Whispers of the Old Gods is available for Windows, Mac, iOS and Android.