The Staff of Magnus

Once you've reached the rank of Warlock, Ajira in the Balmora, Guild of Mages will tell you about the Staff of Magnus.

The staff is located in the cave of Assu, on the slopes of Mount Kand, northwest of Molag Mar. If you look at your paper map, you'll find Mount Kand in the lower southeastern corner of the island. The quickest route is to grab a Silt Strider from Balmora to Suran and on to Molag Mar, or use a Guild Guide to travel to Wolverine Hall and cast an Almsivi Intervention spell from there.

From the Silt Strider, head north. Take the north road on the first intersection (follow the sign to Mount Kand). On the next intersection take the left road (it goes up the mountain). After you pass the entrance to Mount Kand, Cavern look to the right for a small road, which doubles back to go even higher up the mountain. The entrance to Assu can be found at the end of that road.

The caverns are not too large but contain, along with Dreveni Hlaren, a few Daedroth, a Frost Atronach and another mage. A levitate spell is of great use.