Well, I only started playing around the beginning of the Naxxramus additions, after the Goblins vs Gnomes cards. They have a new wing with new cards now, in the "Blackrock Mountain" expansion. This journal is about the new mode called "Tavern Brawl", where you can win a card pack every week, but you play with different rules. For today and the next 2 days, in Tavern Brawl, every time you play a spell card, you get a minion of the same cost summoned to your side of the board.

There's also recently been the addition of 3 new heroes, but they're really just new skins for 3 of the existing heroes.