The precept in Curse of Naxxramas will be to adventure into a dungeon and face several of Kel'Thuzad's "bosses," each with unique cards and abilities. The progression of this single-player game will probably be similar to the tutorial tree the first time a player starts Hearthstone. Oh, and the goodie: as you progress into the dungeon, you get new cards as well! Also, class-specific challenges will be available. Intriguing and geeky, to say the least. I dig!