13,394 NPCs

Classic reference; current Forever availability is unconfirmed.

NPCLevelTitleZone
Shadow of Doom60Eastern Plaguelands
Deathknight Captain61Naxxramas
Deathknight61Naxxramas
Risen Deathknight61Naxxramas
Dark Touched Warrior61Stable MasterNaxxramas
Doom Touched Warrior61Naxxramas
Death Touched Warrior61Naxxramas
Deathknight Cavalier61Naxxramas
Shade of Naxxramas61Naxxramas
Necro Knight61Naxxramas
Bony Construct61Naxxramas
Stoneskin Gargoyle61Naxxramas
Nerubian Overseer60Eastern Plaguelands
Skeletal Smith61Naxxramas
Unholy Axe61Naxxramas
Naxxramas Combat Dummy1Naxxramas
Dispatch Commander Metz60The Argent DawnEastern Plaguelands
Unholy Staff61Naxxramas
Unholy Swords61Naxxramas
Tesla Coil60Naxxramas
Pack Mule1–2Eastern Plaguelands
Guard Didier60Brotherhood of the LightEastern Plaguelands
Bragok55Flight MasterThe Barrens
Argent Dawn Infantry59–60The Argent DawnEastern Plaguelands
Injured Argent Dawn Infantry59–60The Argent DawnEastern Plaguelands
Eye Stalk61Naxxramas
Argent Recruiter1The Argent DawnIronforge
Plague Slime61Naxxramas
Infectious Ghoul61Naxxramas
Field Marshal Chambers60The Argent DawnEastern Plaguelands
Argent Scout55The Argent DawnUndercity
Jessica Chambers52InnkeeperEastern Plaguelands
Keeper of the Rolls1The Argent DawnEastern Plaguelands
Packmaster Stonebruiser59Brotherhood of the LightEastern Plaguelands
Argent Medic57–58The Argent DawnEastern Plaguelands
Argent Emissary1The Argent DawnIronforge
Mutated Grub61Naxxramas
Spectral Soldier59–60
Skeletal Shocktrooper59–60
Scourge Invasion Minion, finder1Tanaris

Classic reference data from QuestieDB (Forever data, commit c5de61a), with positions on Forever's zone maps. It doesn't confirm that an NPC, location, quest or item is in Forever.