Several screenshots from the upcoming Hearthstone: Heroes of Warcraft expansion Curse of Naxxramas leaked today. These screenshots give some crucial details on the game's first single-player adventure.
Curse of Naxxramas, like the World of Warcraft raid that inspired it, has five wings filled with A.I. bosses. These bosses have some interesting mechanics that make them a little like their WoW counterparts. Baron Rivendare has three horsemen minions accompanying him into battle. Noth the Plaguebringer summons a 1/1 skeleton whenever an enemy minion dies.
Maybe the most interesting boss fight revealed through today's screenshots (via Reddit), though, is Patchwerk. In WoW, Patchwerk was a simple DPS check. If your group couldn't deal enough damage to him before his enrage timer was up, he'd murder everyone. He operates much the same way in Hearthstone. He has no cards in his hand but a 5 damage, 7 durability Hook weapon. It seems he'll just beat on you every round with that Hook until one of you is dead.
Completing each wing by defeating its final boss earns you a new Legendary. For example, beating Frostwyrm lair will unlock the Kel'Thuzad card for your collection. At the end of each turn, he resurrects any friendly minions that died during that turn:
Completing the Construct Quarter actually gives you two Legendaries: Feugen and Stalagg. This midrange minions are decent enough on their own. However, if both of them die in the same match, the player will summon Thaddius. Feugen and Stalagg were Thaddius' minions in World of Warcraft so presumably he's much more powerful than either in Hearthstone.
The leaked screenshots give us a better understanding of Curse of Naxxramas' structure, too. They reveal three modes: Normal, Class Challenge and Heroic. You have to beat Naxxramas on Normal to unlock Class Challenges. Presumably Heroic is unlocked in turn by beating the Class Challenges. Heroic is the term for hard mode in WoW raids so expect a higher difficulty level.
Class Challenges ask players to defeat specific bosses with specific characters. In doing so, you'll earn a class-specific card. For example, Rexxar the Hunter must defeat Loatheb to unlock Webspinner. Webspinner is a 1/1 spider that draws another random Beast card on death.
Because these screenshots weren't released by Blizzard, they probably don't represent the final version of Curse of Naxxramas. Certain stats or mechanics could change. Just keep that in mind when you're checking out the full gallery below.