13,394 NPCs

Classic reference; current Forever availability is unconfirmed.

NPCLevelTitleZone
Dark Keeper Zimrel55Blackrock Depths
Dark Keeper Ofgut55Blackrock Depths
Dark Keeper Pelver55Blackrock Depths
Dark Guard53–54Blackrock Depths
Scarlet Warder53–54Eastern Plaguelands
Scarlet Praetorian56–57Eastern Plaguelands
Scarlet Cleric54–55Eastern Plaguelands
Scarlet Curate55–56Eastern Plaguelands
Scarlet Archmage55–57Eastern Plaguelands
Scarlet Enchanter53–55Eastern Plaguelands
Aquementas54Tanaris
Xavathras54Felwood
Warlord Krom'zar20The Barrens
Cyrus Therepentous55Burning Steppes
Gadgetzan Bruiser57Tanaris
Frenzied Black Drake54Cyrus's MinionBurning Steppes
Chieftain Bloodmaw56Felwood
Overlord Ror51Felwood
Golhine the Hooded60Druid TrainerFelwood
Miblon Snarltooth50Feralas
Watchman Doomgrip55Blackrock Depths
Cloned Ooze50–52Un'Goro Crater
Plugger Spazzring55
Mistress Nagmara54
Innkeeper Adegwa30InnkeeperArathi Highlands
Phalanx55
Private Rocknot52
Lord Banehollow59Felwood
Shadow Lord Fel'dan57Felwood
Rakaiah56Felwood
Grark Lorkrub56Burning Steppes
Blackrock Ambusher56Burning Steppes
Kolkar Stormseer15–16The Barrens
Kolkar Invader16–17The Barrens
Freewind Brave45Thousand Needles
Arathandris Silversky60Emerald CircleFelwood
Maybess Riverbreeze60Emerald CircleFelwood
Maxwort Uberglint42Burning Steppes
Hurley Blackbreath55Blackrock Depths
Enohar Thunderbrew50Blasted Lands

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.