Blizzard have released the first wing of the Curse of Naxxramas expansion for Hearthstone. It’s a single player expansion so you can test your deck against the malevolent undead who roam Azeroth’s most infamous floating necropolis. The first part of this expansion is called, The Arachnid Quarter, and it’s now available for free to all Hearthstone players who step into the necropolis during the Curse of Naxxramas launch event, taking place now through early September (The exact end date is yet to be confirmed).
For more detailed information on the Arachnid Quarter’s you can go here.
Access to additional wings may be purchased using in-game gold or real world currency. After the Arachnid Quarter, the next four wings can be purchased for 700 gold per wing or $6.99 per wing. If you don’t want to use real money you can earn the in-game gold needed to unlock the next wing by completing various quests or emerging victorious from the Arena.