If you didn't already know, Curse of Naxxramas is Hearthstone's first adventure which came out on July 22, 2014. The story is set in the undead city of Naxxramus where there are five areas or "wings" of the map. You get the first area, The Arachnid Quarter, for free upon download of the game. The other 4 regions can be accessed by purchasing them with either gold that is earned in game, or if you're impatient-- real money.
You earn gold in game by completing adventures and defeating boss's. There are 2 difficulty setting in the game: Normal and Heroic. The higher the difficulty, the higher the reward. The further you get in the game, the more challenging the boss battles become. One particularly difficult Boss to beat is Loatheb in The Plague Quarter.
Once you take down Noth and Heigan, the only boss left in the Plague Quarter is Loatheb. At first glance Loatheb may seem a bit overwhelming. While most bosses have a hero power that you must figure out a strategy against, that isn't the case with Loatheb.