The second solo adventure to go into the trading card game, Blackrock Mountain is themed after classic World of Warcraft dungeons. The complete adventure pack is $25, and as an incentive for pre-purchase, Blizzard is dangling an exclusive Molten Core card back for those who take the bait now. You can pre-purchase the adventure only with real money.
Blackrock Mountain will release in April over a span of several weeks as new wings are opened. It will contain five wings and 31 additional cards. Players can eschew pre-purchasing it in favor of buying the wings separately.[Source: Hearthstone]