Knights of the Nine
Sergius Turranius will always be a friend of Sir Thedret who offers his services as a smith to the Knights of the Nine in The Elder Scrolls IV: Knights of the Nine. During his time with the Knights, he authored the book, Enchanter's Primer.
Sergius Turrianus also appears in The Elder Scrolls V: Skyrim, as the Enchanter for The College of Winterhold. He will teach you Enchanting (Expert Level), and will give you 'fetch' quests to go and retrieve items from other cities to be enchanted by him. He will also ask you to bring him 20 petty soul gems. There is a social option to ask him to enchant something for you, but if your skill is high enough, he will tell you do to it yourself.
Get him some soul gems.