Blizzard first announced that its popular free-to-play collectible card game _hearthstone would be getting an "Adventure" mode a couple of months ago, but few details were given.

At PAX East over the weekend, however, the company unveiled Curse of Naxxramas, the first of these single-player modules to hit the game, and explained how it fit into the whole _hearthstone experience.

Based on the World of Warcraft dungeon of the same name, the Adventure module -- which will be available across all versions of hearthstone, including its iPad incarnation -- will see you fighting through the five wings of Naxxramas and defeating the bosses there, including giant spider Maexxna, "fungal horror" Loatheb, and the abomination Patchwerk. Each boss has its own unique cards to use against you, so be prepared to face some unexpected abilities and minions in your battles.

Naxxramas has its own unique game board, too, complete with new clicky things in the corners to fiddle with while you wait for your turn.

But why bother playing a single-player mode in a game specifically designed for online duelling? Because of the rewards, of course; beating the bosses of Naxxramas will reward you with new cards to add to your collection and decks, and beating each of the dungeon's five wings will reward you with guaranteed Legendary cards. Not only that, but class-specific challenges that pop up as you explore the dungeon and take on its challenges will provide the chance to pick up some class-specific cards, too, so if you want to strengthen a favorite class deck, a quick crawl through Naxxramas will be a good means of doing that -- so long as you can complete the challenges, of course.

Once Curse of Naxxramas is released, the five wings of the dungeon will open up one at a time over the course of five weeks. The first will be available for all hearthstone players to jump into for free; the remaining four must be purchased using either in-game gold or real money. As each new wing is released, its unique cards will go in to the Arena mode, too, even if you haven't earned the cards for your own personal collection as yet.

There's no release date or pricing information for Curse of Naxxramas just yet; this being Blizzard , it'll be out whenever they think it's ready and not a moment before. Keep an eye on hearthstone's news page for the latest -- and while you're there, be sure to give the game a shot if you haven't already, as it's really rather good.