Skyrim:Restoration Ritual Spell

Quick Walkthrough
#Talk to Colette Marence.
#Talk to Augur of Dunlain.
#Pass the Augur's test.

Detailed Walkthrough
Find the Augur of Dunlain

Once you reach level 90 in the Restoration skill and have completed Good Intentions, travel to the College of Winterhold and speak with Colette Marence. Ask her if you can learn anything more about Restoration magic. She will tell you to go speak with the Augur of Dunlain down in The Midden.

Pass the test

The Augur of Dunlain will give you a test. Once you have stepped into the "light", all non-quest items will be taken from your possession. The Augur will summon one ghost, shortly followed by another, and finally a third; each will attack you with destruction spells and/or weapons. It is not possible to attack these ghosts; your only goal is to keep yourself alive using Restoration magic. Alternatively, the Become Ethereal shout will leave you invincible for most or all of the test, depending on how many words have been unlocked. If you are still alive when the test stops, you will receive your items back and the Bane of the Undead spell. You will also be able to buy the Guardian Circle spell from Colette Marence the next time her inventory resets.

Notes
If your Sneak skill is high enough, you can simply crouch before the first ghost notices you and remain hidden for the duration of the test.
The ghosts favor frost spells, so if you are a Nord or vampire—or better yet, both—this will be very easily accomplished.
You can take along one item (for example, a ring with double magic resist 45%) to the test by dropping the item and then holding it in the air while going to the light.
If you have completed Bound Until Death from the Dark Brotherhood quest line, you can summon the Spectral Assassin while crouching and the test will be passed after a few seconds.
Appearance of the Guardian Circle spell upon the completion of this quest can be bugged. See Guardian Circle for fix.
You can give as many items as you need to your follower, and step in to the light. Then, before the first ghost notices you, talk to your follower and trade items to retrieve them. Items with Fortify Restoration, Fortify Sneak, and/or Resist Frost enchantments would be good choices.
Unlike other ritual quests, this one grants you the first spell directly rather than as a spell tome.

Bugs
 
Removing some of the items from your inventory before stepping into the light may help avoid the bug.
 
 By using the console, the quest can be set to an earlier stage where the faulty script does not occur:  .
 
 
 Reloading a save previous to the ritual will solve this problem.
 
This causes the spell tome Mass Paralysis to be available for purchase upon quest completion.
The bug doesn't prevent the Dragonborn from completing the Alteration quest at a later date.
Bug fixed by the Unofficial Skyrim Patch.
 
Reloading a previous save and interacting with her merchant inventory prior to starting the quest seems to fix this.
This may occur because the game incorrectly flags the Alteration ritual quest as being completed instead of the Restoration quest. You can buy the Guardian Circle spell directly after completing the quest because the game also gives her the tome directly so you wouldn't have to wait until her inventory resets, but once it does reset, the book will never appear again. 
 You can fix this with the console command   .
 

Quest Stages