22 transmog appearances in Naxxramas.
AnarchyOne-Hand
Betrayer of HumanityTwo-Hand
Calamity's GraspOne-Hand
Cape of the Unworthy WizardCloth BackCloak of the DyingCloth Back
Death's BiteTwo-Hand
Drape of the Deadly FoeCloth Back
Envoy of MortalityRanged
Hammer of the Astral PlaneOne-Hand
Journey's EndTwo-Hand
Kel'Thuzad's ReachOne-Hand
Last LaughOne-Hand
Leggings of Mortal ArroganceCloth Legs
Nerubian ConquerorRanged
Sinister RevengeOne-Hand
Staff of the PlaguehoundTwo-Hand
The SoulbladeOne-Hand
The Turning TideOne-Hand
Torch of Holy FireOne-Hand
Voice of ReasonShield
Wall of TerrorShield
Wand of the ArchlichRangedSign in with Battle.net to see which of these appearances and collectibles you already have, and which of your characters can still loot Kel'Thuzad this reset.