So I completed the Conjuration Ritual quest, but the Unbound Dremora won't leave the college.

He's supposed to leave after 999 seconds as the spell states, but he just stays there forever.

I can't finish the mages quest line because he has a particular hatred for Ancano and won't stop attacking him.

Any help?

Sounds like its bugged out, reload an early save just before you summon him/before the quest, if you don't have any saves for that...then I guess there isnt anything you can do, quests [censored], like alot of other ones, might need to..."ignore" it.

Googled around and it seems to happen to everyone.

I have plenty of earlier saves as I keep a stockpile of 10 before I start to overwrite, but I tried it a few times and he still stays here.

Pretty damn annoying.

I managed to complete the questline though, Ancano managed to flee and the Dremora went back to the roof.

He's still there but he only attacks dragons, which I guess is kinda helpful since he's invincible.
Still want this to be fixed though.

Happened to me a few weeks ago too. I guess he's still up there but i've not checked for a while.

The last i knew of him was hearing him attacking a dragon also, while i was in the courtyard below.

If you blow the Dremora Lord off the roof with a shout he'll start walking around the campus and inside the college like he owns the place. Every once and a while he'll get a whiff of weakness too.

I once even saw mine in the library - like he's reading - pretty funny.