See Nightbane quest chain for a summary of this quest chain.
Archmage Alturus at Deadwind Pass wants you go into Karazhan and speak to Wravien.
Your name is getting around, <name>. You've made your way into and out of Karazhan - more than most mortals can claim.
I need to ask a special favor of you. As part of our research, the Violet Eye has been trying to track down Medivh's own journal.
Unfortunately, none of the agents we've sent inside have come out. Wravien was the last to be sent; see if you can find him and see about any leads on the journal.
A vast wealth of information... I could spend years here! I'm sure Dalaran will understand...
You can get this quest outside Karazhan when you are honored with the Violet Eye.
Wravien can be found in the large hall after Curator. The mobs around Wravien will auto-clear about half an hour after the Shade of Aran has been defeated.
This is part of the Nightbane quest chain: