This will be the sticky thread where you can check what can be found where.
If you want to get a first impression on this guild, feel free to check out the guild spotlight application that we sent to Zenimaxx. The fetchers didn't post it, but it's nonetheless a good place to start.
If you want to interact with Telvanni nobility, especially the Archmagister and the High Council, there are some things that you should be aware of. Please make sure you read them first before an immersion-breaking situation or an on-the-spot execution occurs.
If you are a Telvanni wizard and want to fit in, here are a few questions (and example answers from Vivicah's point of view) that every Telvanni who's not in a mushroom tower on Vvardenfell should have answered for themselves.
If you want to play a powerful and antisocial Telvanni wizard, or are wondering how a guild made out of those could ever have social interaction, you should totally read Valorin's notes about Being Neloth Telvanni.
If you want to read up the ranks, you can do so here.