- Speak with Mirabelle in Winterhold College.
- Travel to the ruins of Mzulft and listen to Gavros Plinuius.
- Make your way to the Mzulft Aedrome and recover the Focusing Crystal from a levelled boss.
- Find a key to the Oculory. Open the door to the Oculory and meet Paratus Decimius.
- Speak to Paratus and follow his instructions.
- Align the beams of light of the Oculory, and activate it.
- Speak to Paratus again.
- Leave Mzulft and return to Savos Aren in Winterhold College.
- Help Savos and Mirabelle bypass a ward.
- Watch the scene, exit to the College courtyard, and protect Winterhold.
Arch-Mage Savos Aren has mentioned that Mirabelle was talking about the Staff of Magnus not too long ago. Ask her what she knows about it and its whereabouts. She will direct you to Mzulft, as a group calling itself the Synod have approached her and asked her about the location in a secretive manner.
As you enter Mzulft, you will find one of the members of the order; he will mention the Falmer and die. His corpse yields a key necessary to continue into the ruins. Mzulft is a fairly lengthy Dwemer Dungeon with many Dwemer items and the usual mix of dwemer automatons, as well as a few encounters with Falmer and Chaurus.
As you reach the Aedrome, you will meet a levelled boss Falmer with a Focusing Crystal in his possession. Defeat him and loot the Crystal, which will become necessary once you enter the Oculory. However, your way is barred by a locked door. Turn back - straight across from the locked door (straight east from the locked door, in the same room, there is another, unlocked, door) - and follow a little further into the ruins, to find a room with dead Falmer a levelled Dwemer Centurion or other boss automaton. Destroy the automaton and loot the Key to Oculory from a chest in the same room.
Head back and open the locked door; behind which you will find another closed door. No key is required to open this door, though, as you will hear a voice from the other side once you approach it. This is Paratus Decimius, another imperial mage, who will assume that you're Gavros and then open the door. Talk with him and explain what you're looking for, deciding how much you want to tell him. Finally, tell him that you've recovered the Focusing Crystal: he will then lead you to the Oculory.
You will reach a room with a huge spherical device in it and a domed ceiling. The ceiling has three horizontal blue bands, with a large mirror on each band. Paratus will lead you to the top, and will tell you to place the Crystal in the device, at which point three reflected beams of light will be generated from the beam entering right at the top of the dome. Next, you need to focus the Crystal by casting Fire and Frost spells on it until each beam reflected by the device is pointing to the middle of one of the bands, one beam for each band. Finally, you have to use the buttons on a pedestal overlooking the device to rotate the bands in the ceiling so that the mirror on each band intercepts its respective light beam. Each button controls one of the bands.
When you're done, Parathus will comment that this is not what he was expecting; go down to see what he's talking about. On a wall under the pedestal is now shown a map of Tamriel (mostly just northern provinces and Cyrodiil). Parathus will tell you that the Synod members were searching for a way to scan the continent in order to find powerful sources of magic. The map is showing only two major magical sources: one in the College of Winterhold (it's the Eye of Magnus, but you don't have to tell him that if you don't want to), the second in Labyrinthian. Parathus will presume that the Staff of Magnus is in one of the two places, but will mostly complain about the College interference. As you leave Mzulft, you will receive another vision from Nerien, urging you to return to Winterhold immediately, where you will be called upon to take swift action.
As you enter the Hall of the Elements, you'll see Savos and Mirabelle looking at a strange magical barrier, blocking your way to the Eye. It seems that it's a deed of Ancano, who's doing something with the orb. Mirabelle will start casting a Destruction spell on it; Savos will ask you to do the same and will then join you in casting. When the ward is dispelled, go with your superiors inside the Hall. You'll see Ancano casting a spell on the Eye; as Savos approaches him, he won't be interested in conversation but simply renew his effort on the casting; the intense magical energies will blow you away and you will pass out.
When you regain consciousness, you will see Mirabelle sitting nearby, breathing heavily. She will also ask you to search for the Archmage, starting the Containment quest.
