Well, I am at work right now so I cant give you every detail, but I am in the University. The last mages guild mission I did was to find this necromacy book and figure out where they are located. So I found the book, and found out where they were located and went back to the arch-mage. So the book quest was completed. Next he wanted me to go to the location the book said and find out more information. He marked Dark Fissure on my map (east of Imperial City) and I set off to kick some ass. Now, a new quest entry was never made for this nor is there a dialog option about Dark Fissure in the conversation tree, but the arch-mage comments everytime he sees me asking 'have you gone to the dark fissure yet?'.
Anyways, I went there and killed all the necromancers. I searched all the chests and etc, and went back to talk to the arch-mage. None of the dialog options are for the Dark Fissure, and I dont know what I missed.
Edit: maybe I need to talk to someone else at the Uni, hmmm