| Lithrac |
Making Brodert Quink a wizard is actually an interesting thing to do, but puts you at risk of losing him, then making it harder for the party to find information on Thassilon until they reach Mokmurian's library (in FotSG).
Otherwise, may I suggest one of the NPCs I've created for my S&S group as a possible cohort? Her name is Gaige Firehair, she's a gnome conjurer freshly graduated from Korvosa's academy and her passion is for ancient empires (Ghol-Gan in my campaign, but it's easily changed to Thassilon). She's very talkative and curious.