Hearthstone will be getting a new mode this month, titled "Tavern Brawl." 

The Hearthstone Blog detailed the new mode, which will be added with a patch sometime in mid-June. Tavern Brawls will be week-long events that introduce unique rule sets. It lists a few examples like using preset decks, crafting a new deck with special guidelines, or buffing certain types of minions. You can go up against strangers or challenge a friend to a Brawl. 

You'll need to be level 20 to take part in Brawls, and each one will last about a week with a couple of days in-between. The first Brawl entry will be free, and you'll be rewarded with a free card pack when you win your first game. Blizzard didn't detail what the regular cost of entry will be.

The patch that introduces Tavern Brawls will bring a few other changes as well. It appears to be when Blizzard will roll out new heroes, starting with the previously announced Magni Bronzebeard. The blog also teases two more heroes. 

Finally, the Collection Manager is undergoing some revisions. Card backs will be moved to that menu, letting you set a Favorite as your default card back, and also assign card backs to particular decks. That menu will also house the new hero selection options, and you can assign different heroes to different decks.