Blizzard today announced Hearthstone: Heroes of Warcraft, a new free-to-play collectible card game set in the Warcraft universe. In a first for Blizzard, it will be available on the iPad in addition to the Mac and PC. It appears that players will be able to play multiplayer games across platforms. Set in the World of Warcraft universe, each Hearthstone deck will revolve around heroes of nine of the MMO's classes. At least 300 cards will be available at launch, and you'll be able to earn or buy packs. Also, you'll be able to put together your own decks and be able to "disenchant" duplicates and craft better, presumably original cards from them. The competitive side of the game will feat