The Eye of Magnus

Into the Eye of the Maelstrom
Approach the College of Winterhold, now caught in an increasingly unstable maelstrom of magic. Equip the Staff of Magnus, and use it to force your way across the courtyard and into the Hall of the Elements. Ancano is waiting within the mass of crackling and ethereal discharge. Face Ancano and attack the Eye of Magnus and the Thalmor traitor directly.

Upon arriving at the Hall of the Elements, Ancano is well aware of your presence. The mad elf spots you and Tolfdir, taunting you and crowing that he’s so far beyond your pitiful attempts at magic that you cannot even touch him.

Unfortunately, this is true, as you both find out when Tolfdir’s aimed fireball dissipates harmlessly. The old mage has just enough time to tell you to bring out the Staff of Magnus and use it on the Eye before an enraged Ancano strikes him—and anyone else (such as Followers) in your vicinity—with a Mass Paralysis spell, leaving you standing alone.

Ancano decides to finish you himself, opening the Eye of Magnus and tapping into its full and incredible power.

Defeating Ancano
While Ancano opens the Eye, he’s still invincible. Wait until the Eye is fully open. When this occurs, a casting from your Staff of Magnus absorbs its energy, and the Eye begins to close.

Now is the time to thwart Ancano! Strike often and hard, because eventually the Eye reopens and Ancano becomes invincible again. When the Eye is pried open a second time, several Magic Anomalies are also let loose. Although you must deal with them, their presence has the potential to be very useful, as the Soul Gems they drop can recharge the staff if it is out of charge.

Use the chamber’s topography to your advantage, keeping your distance from Ancano, which gives you more time to maneuver around his spells. If possible, stand behind one of the chamber’s many pillars, or the Eye itself, blocking the full force of Ancano’s attacks. Your own summoned creatures can also provide temporary distractions.

Switching between Favorites and utilizing your different weapon combinations is imperative, too. However, equip the Staff of Magnus in one hand to remove Ancano’s invulnerability and power up a spell in your other hand, readying it for the moment you can hit Ancano.

Then immediately switch to spells in both hands to deal the maximum amount of damage before the Eye reopens. Keep this up, and you may rid the College of this enormous anomaly!

It is possible to wait for Ancano to fight with Magic Anomalies and kill him with one power swing melee attack.

The Nick of Time
With the hated High Elf now dispatched for good, you can return to Tolfdir. He is thankful you have stopped Ancano but has no idea how to dispel the gathering crescendo of power that the Eye of Magnus is magnifying. Fortunately, Quaranir has appeared just in the nick of time.

Speak to him, and although he is as cryptic as ever, he tells you that the Psijic Order always believed in you, and your actions have proved that you are ready to lead the College of Winterhold. Now that the Eye has grown unstable, it may not only destroy the College, but also the entire world!

Ancano’s actions proved that this world is not ready for such power; Quaranir prepares to secure the Eye. The Psijic Order will maintain the Eye for now, and he summons his brethren, Gelebros and Tandil, to perform a binding ritual. The monks and the Eye soon disappear from this world.

Bugs

 * If you encounter a Dragon before entering the college and do not kill it, the cuts scene will fail to start, rendering the quest uncompletable. After Defeating Ancano, it is possible to go back outside to kill the dragon. Upon reentry, the cut scene with Tolfdir will start after you walk up to him (confirmed on Xbox 360).
 * Upon completing this quest it is possible to acquire double the rewards, two (2) arc-mage robes & two (2) arc-mage keys. This has been seen on the PS3 though it is unknown on other platforms and is likely a rare occurrence
 * Upon completing this quest, you receive the achievement on your 360. If you open this achievement while talking to Tolfdir you will get stuck in the conversation and won't be able to exit for about 2 minutes.