After talking to the Arch-mage, he’ll send you to do some research in the Arcanaeum. Talking to Urag gro-Shub will tell you about the missing books and the man who took them. Your job will be to go get the books and bring them back. When you’re ready, head out for Fellglow Keep.
When you get there, you will be greeted by some necromages. They will generally summon some form of atronachs and then attack with cold magic. Make your way into the tower and down to the basement. Inside, the first enemy you will come across is a mage and a pet frostbite spider.
You’ll eventually come to a set of stairs off to the side that will lead you up to a room with a locked door. Behind the door will be a decent chest and some good loot scattered around. Make sure you loot it before you head back onto the path. Make your way down to the cell block.
You’ll cross a den like area and come across a couple more mages. Kill them and make your way to the next holding area. In one of the cells is the Mage from the College who you can choose to save or not. Pulling the levers in the middle will open up the cells but if you open the wrong one, you’ll release wolves. There is an enemy mage here who will try to release those wolves so try to kill the mage quickly.
After talking to your new friend, he may follow you – provided you chose to let him. He’ll bring along either his familiar in the form of a wolf or his fire atronachs, which can be quite useful. Continue through the side door and you’ll come to what looks like a shooting range with a few mages training. Kill them and head through the doorway to the left.
Make your way through some dusty rooms. Eventually, you will come to a room fill with skeletons. Kill them too and continue through the small tunnel. Kill the mage and the skeletons that are coming out of the coffins. Exit into the small tunnel and go through the door there.
In the next zone, you’ll come to a summoning area. Watch out for the fire atronachs here.
Make your way through the hallways beyond and you’ll bump into more Atronachs and Mages. Kill them all until you come to a rather large room. From here, you can continue on to fight with the final boss (after going through the library) and later, you will return to this point to take the shortcut out.
Cut through the libraries and make your way through a few more deserted hallways until you come to a large spiral staircase lit by candles on either side. At the top, is the final room. Go inside and confront the Mage there. She will summon a Frost Atronach and transport all over the room. Otherwise, she’s just another mage. Kill her and her atronachs. Collect the books scattered around the room on the pedestals.Exit Fellglow keep through the trapdoor and find your way back to the college. Head down to the Arcanaeum and return the books.