| Arachnid Quarter | Plague Quarter | Military Quarter | Construct Quarter | Frostwyrm Lair |
The Frozen Heart of Naxxramas, unlocked by completing the first four quarters. Two bosses. Neither boss has any trash to clear, though Kel'Thuzad has a three minute event every time he is engaged that could be considered trash. Sapphiron will severely test the healers of new groups. Kel'Thuzad is considerably easier on 10-man difficulty but is arguably the hardest boss in the instance on Heroic difficulty and will require the tanks, healers and DPS of new groups to play well to succeed.