Hearthstone's first single-player expansion Curse of Naxxramas will add dozens of new cards to the game. Let's take a look at the full list of new additions.
Nine of the new cards are class-specific. They can be unlocked through Class Challenges, which ask players to beat certain Naxxramas bosses with specific characters. For example, Rexxar the Hunter has to defeat Loatheb to get his new card. Each class has their own challenge and card reward:
Druid: Poison Seeds (spell) - Destroy all minions and summon 2/2 Treants to replace them.
Hunter: Webspinner (minion) - Deathrattle: Draw a random Beast card.
Mage: Duplicate (secret) - Secret: When a friendly minion dies, put 2 copies of it in your hand.
Paladin: Avenge (secret) - Secret: When one of your minions dies, give a friendly minion +3/+2.
Priest: Dark Cultist (minion) - Deathrattle: Give a friendly minion +3 Health.
Rogue: Anub'ar Ambusher (minion) - Deathrattle: Return a friendly minion to your hand.
Shaman: Reincarnation (spell) - Destroy a minion, then return it to life with full Health.
Warlock: Voidcaller (minion) - Deathrattle: Put a Demon from your hand into the battlefield.
Warrior: Death's Bite (weapon) - Deathrattle: Deal 1 damage to all minions.
The expansion also introduces several Legendary minion cards. They're based on the final bosses of Naxxramas's five wings. Presumably you unlock them by defeating them in battle. In the case of the Construct Quarter, there are actually three Legendaries to gain: Feugen, Stalagg and Thaddius. Here's the complete list of Legendaries, along with the wings they're located in (via Hearthstone's official Facebook page):
Baron Rivendare (Military Quarter): Your minions trigger their Deathrattles twice.
Loatheb (Plague Quarter): Battlecry: Enemy spells cost (5) more next turn.
Maexxna (Arachnid Quarter): Destroy any minion damaged by this minion.
Kel'Thuzad (Frostwyrm Lair): At the end of the turn, summon all friendly minions that died this turn.
Stalagg (Construct Quarter): If Feugen also died this game, summon Thaddius.
Feugen (Construct Quarter): If Stalagg also died this game, summon Thaddius.
Thaddius (Construct Quarter): Summoned when Feugen and Stalagg die. No special abilities of his own, but he has 11 health and 11 attack.
The rest of the Naxxramas cards are minions ranging from Common to Epic. Like the Legendaries, these cards are Neutral so you can use them no matter what class you're playing as. You can check them out in the gallery below along with the Class cards and Legendaries mentioned above.
Curse of Naxxramas will debut in North America on PC, Mac and iPad on July 22nd. European gamers will get their hands on the expansion on the following day. Blizzard plans to release Naxxramas one wing at a time over five weeks. You can check out the full release schedule and price list here.