Curse of Naxxramas is Hearthstone's first adventure. Set in the Scourge necropolis of Naxxramas, Curse of Naxxramas is a five-wing adventure, with each wing representing one of the wings of the World of Warcraft Naxxramas raid instance. The adventure features a total of 30 new collectible cards, gained through completing various aspects of the adventure and a new battlefield. The wings of the adventure must be purchased with gold or real money before they can be played or their cards can be collected. The adventure itself comprises a series of unique boss battles distributed among the wings. Players are able to tackle bosses in several different difficulty modes: the basic Normal mode, the grueling Heroic mode, or Class Challenges bringing strategic twists to existing boss encounters using special pre-selected decks.