TriangleTooth's Missing Characters
Step #199 in the Total Overhaul list
Featured in Mod Lists:
Adds new NPCs who were mentioned by dialogue but had no physical presence on Vvardenfell. Also gives them new unique dialogue lines that fit seamlessly into the vanilla game.
Those following a mod list (or if you're using Tamriel Rebuilt in general) should use the "No Nolus" plugin.
Ttooth's Missing NPCs - No Nolus.ESP