At lower levels, it is one of the only side quests you will get from Neloth. He will reward you with a random generic staff from his own collection. Retrieve the staff from the specified dungeon and return it to Neloth.
Skyrim is far more likely, as there are considerably more potential locations there. If it is possible, I'd like to get some ideas on how it might be accomplished. First of all, I'd like to know if it would be possible to get staves and shields to show on your character's back in third person. Finish him and continue through the passage until you exit to Skyrim. Pull the lever and enter the room to be waylaid by Estormo.
Head up some stairs until you come to a barred gate with a lever on the right. Once you have the staff, head for the exit at the back of the chamber.
