Blizzard announced the “Blackrock Mountain" expansion coming to Hearthstone (Free) back during PAX East, and now you have the ability to pre-purchase the expansion ahead of its release, and get an exclusive card back for pre-purchasing. If you buy it for $24.99, you’ll get the Molten Core card back for free, which can’t be obtained otherwise. You will, of course, be able to buy the expansion with 700 gold or in multiple wings for $6.99 each, just like “Curse of Naxxramas."
The expansion will release in April, though we don’t quite have a solid release date yet. You’ll get 31 cards for beating the expansion, so if you’re looking for some singleplayer stuff to enjoy in the game along with getting some rad new cards for your decks, you might want to pick this one up. And if you preorder, you get the Molten Core card back immediately.