Karazhan attunement is a chain to get The Master's Key, which allows entrance into the 10 man raid instance.
Archmage Alturus, at the south end of Deadwind Pass has been studying the area known as Karazhan. There are a lot of restless spirits in the area, and he would like to study them. He is an old man, however, and not up to the rigors of collecting the essences of the spirits first-hand. You, being young and spritely, volunteer.
Alturus is also trying to get an imprint of Karazhan's energy, but is not getting useful results from the surface. There are, however, two places his crystal would get useful results - an underground pond, and a well in one of the cellars. Unfortunately, those places are guarded by ... you guessed it, restless spirits that he is not up to warding off. Since you're retrieving spirit goop for him anyway, you volunteer to do that too.
Studying the crystals and essences you brought back, Alturus has come to some worrying conclusions. So worrying, he tells you about a very select group - the Violet Eye. He asks you to take a message to another member of the Violet Eye - Archmage Cedric.
You find Cedric in the south end of ruins surrounding Dalaran.
After traveling to Dalaran and finding Cedric, he decides that since you know so much already anyway, he'll use you to get back into Karazhan and investigate the demonic emanations coming from within (not to mention find out what happened to their lost agents). He recently figured out that Khadgar is alive in Shattrath City and sends you to get the key from him.
Khadgar reads Alturus' report and is equally troubled by the news. Unfortunately, he doesn't have the key anymore, thinking it would be safer scattered into pieces across Outland instead of on his keyring. The first piece is in Auchidoun, which since Khadgar's last visit has been taken over by the Shadow Council. He asks you to go get it.
Fortunately, the key fragment was still there and still safe and you bring it back to Khadgar. Relieved that you ended up having worthy enough eyes to see through his spell, he asks you to recover the 2nd fragment that's probably somewhere in Coilfang Reservoir (since he threw it in a lake), and the 3rd fragment from a room in Tempest Keep that seemed nice at the time.
You come back with the last two key fragments and Khadgar seems genuinely impressed. He sticks the three fragments back together again but notes that there's still a problem. The key needs Medivh's consent in order to be able to open Karazhan. Death not being a problem for Khadgar, he asks you to enter the Caverns of Time and convince Medivh to let you into his home.
You head to the Caverns of Time and help Medivh open the Dark Portal and start three of the most destructive wars to have ever occurred on Azeroth. Then you show him the key. Medivh, being the powerful wizard he is, recognizes Khadgar's key even though he hasn't given it to him yet and seems to remember something about you in the future. He decides he wants to keep Khadgar's key so he can give it to Khadgar, so he gives you his key instead.
You head back to your own time and give Khadgar Arthas' key. Confused about where his key came from in the first place, Khadgar shrugs it off and sends you on your way back to Karazhan to check out the place.
Impressed that he tagged you as a delivery boy and you came back with a way to break through the seal (that they couldn't), Alturus asks you to head on in and find a log of one of their agents who died awhile back, Keanna. He's not sure where the log might be, but there's a blacksmith who used to be on the payroll that might know.
Fortunately, the blacksmith was still around, although he seems to have lost some of his memory, and all of his life. He remembers the name Keanna though and bashfully confesses she spent a lot of time up in the guest chambers. You head up there and find her small red book.
You take the book back to Alturus who skips to the end and confirms that he was right all along. Apparently, there's a demon at the top of the tower and since you're the only one with the key, you have to go kill it. After huffing it to the top and killing Prince Malchezaar, you head back down to Alturus. Delighted, he confirms that things are back to normal (only undead and evil spirits now). Assuring you that Dalaran really is cool despite what you think, he sends you back to his boss.
Having already talked to Alturus through the great void, Cedric gives you one last task: to forever guard Karazhan as a member of the Violet Eye (since you're the only one that can get in). You graciously accept the Violet Badge before selling it to the nearest vendor.
Karazhan quest progression
Karazhan stealth attunement
It is a somewhat lengthy chain requiring groups and so being able to solo any aspect of it will possibly quicken the overall time to attune. Here will be described the actual attunement process, describing which can be soloed and how.
Starting at Karazhan
Go to Karazhan and get the two quests, one which will require you to collect some essences that drop off the mobs, and another which will require you to get to two scrying points. The essence will require killing a lot of the mobs, and you can pick and choose your points. The two scrying points are in the two cellars, and both can be stealthed to with relative ease. One is a well, and the other is a river. After completing both quests, the quest chain will have you travel to the Alterac Mountains before continuing with Khadgar in Shattrath.
Return to Shattrath and the First Fragment
Go to Khadgar who will give you the quest to get the first fragment from Shadow Labrynth. This is not soloable, and the fragment is at the very end behind Murmur. As of the patch 2.0.7, you can no longer buy your way into a finished instance and must do this instance yourself with a group.
Finding the Second and Third Fragment
This is one quest given by Khadgar, who instructs you to get both the second and third fragment before returning to him.
To get to The Steamvault fragment, you will need to be careful of the pats and the bog giants, who detect stealth. Move your way to the first boss. Right before the first boss, there is a pool on your right side, the fragment is at the bottom of this pool. There are no mobs in the vicinity so once you are there you can safely retrieve the fragment. As of patch 2.0.7, retrieving the fragment will summon an elite monster that can be soloed if prepared for. Bring healing potions and bandages. You should be able to duo this easily.
The Arcatraz fragment is trickier to acquire, but it is possible. You will either need the key to Arcatraz or have 350 lockpicking. Druids will likely not be able to solo this. Your first step is to move past the first room, which requires a bit of timing. You will have to move past the two blood elves and the infinitely incoming mobs. There will be occasional breaks that you can take advantage of if you do not have Master of Deception. Hang to either the left or right side, avoiding the center completely. Once you are past this tunnel, hang to your right side. If you had to use a vanish, wait for it to cooldown as you will need it.
The next objective is to get to the top of the staircase. Be wary of the corpses, as non-elite adds will spawn if you get too close. Move past the various pats onto the staircase, sticking to one side as there is a single pat that goes down the middle. Wait once you hit the top of the staircase as you will need your cooldowns for vanish, sprint, and cloak of shadows if you used them.
The next step is to get past the tunnel, which has two corpses which will spawn adds, as well as a sentinel who appears dead, but will attack you as you get close. The idea here is to move straight down the middle, sprinting while stealthed, using cloak of shadows just before you enter the tunnel, and vanishing if the lightning bolt from the sentinel breaks stealth when you hit the other side. This requires you to be ready to do all these things very quickly, so be prepared.
Once you are on the other side, hang to the right side of the wall, a voidwalker will patrol between the center of the room and the fragment. He is very slow at patrolling, so wait for him to get out of distance. When you loot the container, a mob will be summoned that has the fragment on it. You must be prepared to kill it, so have healing potions and bandages ready. Be careful of the pat and bring a friend if possible. If you wish to attempt walking out you are welcome to, but waiting for the voidwalker to patrol away again and then hearthing is a safer method.
The Black Morass
You are now tasked with convincing Medivh to complete the key. This requires speaking to him after the Opening of the Dark Portal has been completed in the Black Morass. As of patch 2.0.7, you can no longer enter a finished instance and must complete this with a group.