Oblivion:Skingrad Recommendation

Quick Walkthrough
# Speak with Adrienne Berene. She asks you to obtain some notes from a mage that she forced to practice outside of the guild.
# The other mages will fill you in on the details of where Erthor stays and why he stays there.
# Head to Bleak Flats Cave and seek out Erthor.
# Once Erthor is located, kill all the zombies and return to Adrienne with him for your recommendation.

Detailed Walkthrough
Skingrad Mages Guild
Speak to Adrienne Berene in the Skingrad Mages Guild for her recommendation. She asks you to help with finding some notes she lent to Erthor. She suggests speaking to the other mages in the guild, as they may have some idea where he is. Speak to any of the other mages about Erthor. They haven't seen him in a while but he is usually out in Bleak Flats Cave, west of Skingrad. Druja in particular can give you a more detailed location - northwest of Skingrad - and mark the location on your map. Druja suggests you remind Adrienne of this location.

A Terrible Guild Master
Speak with Adrienne and remind her about Bleak Flats Cave. She will send you to the cave to fetch Erthor, giving you a Weak Fireball spell for assistance. The cave is relatively small; besides Erthor there are only seven Deranged Zombies present. These are leveled zombies that drop a unique form of bonemeal instead of mort flesh. You will have to clear out the cave in order to get Erthor to leave and follow you back to Skingrad. Return with Erthor to the Mages Guild and speak with Adrienne again to confirm your recommendation.

Notes
If you want to steal Erthor's stuff but don't want to make a return trip to the cave, lead him around a corner and tell him to wait before taking it. If Erthor catches you in the act, you will be suspended from the guild.
Don't be afraid to let Erthor return to Skingrad by himself. He is able to make it back safely. Be sure first, however, to follow him up the side tunnel that leads from his hiding place. He will need your help to open the rock wall at the end of this passage. Just pull on the lever to the left of the wall to open it.
If you are at a low level, Erthor is a great ally because he is a relatively strong mage and essential. He can help you kill the zombies in the cave if you start by sneaking past them; you can also have him follow you to other locations.
At one point during development, this quest apparently had an option where Sulinus Vassinus could be asked to complete the task for you. The Journal Entries, NPC actions and dialogue options are all still present in the Construction Set; the Prima Official Game Guide also claims that "Sulinus Vassinus will actually do the quest for you." However, it is impossible to trigger any of these options in game, perhaps because the developers intentionally disabled them.

Bugs
 
If you can remember how many zombies you killed the first time, kill just enough zombies to count as seven. This may allow you to leave with Erthor.
  You can use the console to advance the quest by typing  . This makes Erthor follow you even if all the zombies are not dead yet.
 
Reloading the last autosave should trigger the normal events.
 You may enter   into the Command Console to complete the quest and stop Erthor's pursuit.
 
 

Journal Entries
 
† Quest stages 20, 30, and 40 involve a disabled quest option in which Sulinus Vassinus would help complete the quest, see Notes. These quest stages are not accessible.