Image used with permission by copyright holderPublisher Blizzard will announce the next major expansion for its mobile and PC collectible card game Hearthstone: Heroes of Warcraft on March 11, according to a recent teaser sent to top players via postal mail.

　　“There are whispers around the Tavern,” the teaser reads. “Come listen closely and discover the next Hearthstone expansion at a special live-streamed event!”

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　　The note concludes with the address for Blizzard’s official Hearthstone Twitch channel, and advises players to tune in on March 11 at 10:00 a.m. PST to get a first glimpse at the game’s forthcoming update.

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　　Hearthstone expansions are gameplay-overhauling events that introduce dozens of new collectible cards, requiring veteran players to come to grips with an array of balance tweaks and new deck-building possibilities.

　　The first Hearthstone expansion, “Goblins vs. Gnomes,” added 143 new cards to the game’s catalog in December of 2014. The update also marked the launch of a spectator mode that allowed players to watch in-progress online battles during downtime between matches.

　　“The Grand Tournament,” Hearthstone‘s second major expansion, added a collection of more than 130 new cards to the base game in August last year. The Grand Tournament further expanded gameplay possibilities with a new Joust mechanic, along with a new keyword that altered how Hero Power is used.

　　While Blizzard has not yet revealed its plans for Hearthstone‘s forthcoming expansion, players can likely expect several new cards and a handful of tweaked gameplay mechanics to be announced on March 11.

　　Originally released for PC platforms in 2014, Hearthstone: Heroes of Warcraft saw ports for Apple’s iPad and Android tablets shortly afterward. A mid-2015 update added compatibility for iOS and Android smartphones, introducing Blizzard’s free-to-play game to a large chunk of the casual gaming market. As of November 2015, Hearthstone boasts more than 40 million active player accounts.