Return to Karazhan: In the Eye of the Beholder

You may turn this quest into Khadgar either inside of the dungeon after defeating Shade or outside near the summoning stone.

EDIT May 2023: There has been a change where the portal from the library to the entrance is no longer there. I have made several attempts since early 2023 to get an answer re this on the WoW Forums with no result. When I find out if this is a bug or intended, I will alter my posts accordingly for this quest chain.

FURTHER EDIT September 2023: I'm still posting on the forums trying desperately to either get them to respond/fix it/or change where you pop upon release if you die in the latter part of the dungeon. At the moment, Khadgar and Medivh hang around after the last boss is killed for a chat and then Khadgar puts a portal up to "Dalaran". You will either need to take this portal or hearth out and journey back, adjusting the strategy for the Mana Devourers accordingly for the next quest. Fingers crossed someone decides to fix this debacle.

Just a bit of an update on this quest chain since changes have been made in recent patches.

This is the first of the "Return to Karazhan" quests to be done inside Kara. Prior to this are the initial quests you can pick up from Khadgar outside Kara starting with Finite Numbers

You can reset this dungeon in heroic mode as many times as needed to complete the chain in a very short time.

For Return to Karazhan: In the Eye of the Beholder, clear Opera, Moroes (pick up Rusty Keys from the floor near Moroes' corpse), Curator, Medivh, Mana Devourer, and then Viz'aduum.

Along the way grab the crystals for Fragments of the Past - first one is after Opera; exit the stage on the opposite side from where you entered, hug left all the way into the room with the 'backup singers', clear room and go out the door on the opposite side and directly up the ramp. Once through the door at the top of the ramp you're in the audience area of the Opera event; turn right and clear the closest patch of adds in the corner. The crystal is in the aisle between the patron seats.

The next crystal is in the last room on the left (Guest Chambers) in the hall leading to Maiden. You don't need to kill her, just clear trash up the hallway and left side of the room, grab crystal and go back out the way you came in all the way to the entrance from the Opera Event to the The Banquet Hall. Facing the triple archway (looking through towards the stage) turn left and jump over the balcony into Moroes area. If you aim for the line between the tables you shouldn't agro any trash. After picking up the Rusty Key and getting the crystal behind Moroes, there's one elemental to kill in the doorway out then turn hard right and go down the stairs towards Attumen.

You don't need to kill Midnight/Attumen, instead turn left into the Servants Quarter's and in the farthest room is the last crystal for lower Kara and a portal back to the entrance. Take both (in that order). Turn to face the opposite direction you're in after landing from portal and go down to the base of the ramp. Head up the ramp, out the door, turn left and follow up ramp to broken stairs up to Curator. The last crystal is between Curator's feet when you've killed him.

Complete the rest of the dungeon (kill the minimum amount of Mana Devourers in the library on your way through) but after killing Viz'aduum jump off the ship and release. You will pop back at the library. Go up the spiral staircase and use the portal back to the entrance. Leave and hand in the quests, pick up the next in the questline. (Just a heads-up with Viz, as mentioned in other posts; when you land on each ship wait a couple of seconds before you move or it glitches the fight and resets it, also on the second ship wait until pools of yellowy green swirls appear on the ground before damaging Viz again.) EDIT September 2023: having just done this all through again on an alt, you can now one shot Viz without it bugging. The portal to the ship that Viz normally takes to escape from you still spawns and you can take this to the final destination where Khadgar puts up his Dalaran portal after Medivh flies away.

DO NOT RESET INSTANCE. Pick up the next quest Return to Karazhan: Book Wyrms and when you zone back into the dungeon you will pop at the library. Once done, take the portal back out to hand in. Pick up next quest Return to Karazhan: Rebooting the Cleaner and this time reset the instance before entering. You will need to clear Opera and then Moroes for the Rusty Key to access upper Kara to kill Curator but nothing else so it's a quick run. After Moroes run through spiders to the portal in Servant's Quarters. Straight after Curator (pick up the quest item from the ground in the corner of the room near portal) just run back out and down broken stairs to entrance.

Pick up next quest Return to Karazhan: New Shoes (and make sure you loot the box next to the quest giver) but DO NOT RESET INSTANCE. When you zone back in you'll be through the portal at Curator but you can portal back into his room and then just run back (or jump) down the broken stair. There is a door underneath the start of the ramp up to Master's Terrace. If you reset the instance it will be locked and you'll have to kill Moroes again for the Rusty Key. Go through this door and follow along the Terrace to the double wooden doors at the other end (they're open). Through these doors and go slightly to your left is a ramp, go up the ramp and straight ahead is another open wooden door. This brings you to the Grand Ballroom. Go straight ahead and jump over the railing onto the steps down to Attumen. You'll have to clear the trash around Koren to hand in the quest. You can run across to Servant's Quarters again and run the gauntlet of spiders to the portal or, take the stairs up near Koren, kill the two npc's at the doorway, go through and up the stairs which brings you to The Broken Stair with the exit not far away.

For Return to Karazhan: High Stress Hiatus DO NOT RESET INSTANCE. Continue on from where you port in just past Curator's portal and kill Shade of Medivh, drop down the hole for Mana Devourer and then make your way to the Gamesman's Hall. You don't need to kill any of the mobs on the chess board, just hug left when you enter the room, [item=143555] is draped on a chair on the left side of the chess event. It's a quick run back to the library from the chess event to use the portal back to the entrance and leave. Reset the dungeon and re-enter, the [item=143552] drops from trash leading up to Opera and [item=143551] drops from the Opera boss.

For Return to Karazhan: Clearing Out the Cobwebs you can easily do this without resetting after the previous quest providing you haven't killed too many spiders getting to the portal. For classes that can stealth, prowl, or invis it should be fine. Shadowmelding can work (it's only tricky if you've been poisoned) if you stop right next to the portal and once agro has dropped click immediately on the portal in case a spider is nearby. Alternatively, after obtaining the items for Return to Karazhan: High Stress Hiatus, from Opera proceed towards Moroes as previously suggested. Jump over the balcony, kill Moroes, pick up the Rusty Keys and exit as before. Head downstairs towards Attumen, go past Koren and take the stairs leading up to the Livery Stables. At the top of the stairs you're faced with an archway, go through and take the set of stairs up to Master's Terrace and then through the door and on to the entrance. This way you can avoid killing any spiders completely to ensure there's enough for the next quest without resetting. It takes a little longer and there may be a little trash to clear this way but nothing excessive.

Edit 1: I did a little experiment where I ran through to the portal and killed a lot of spiders getting to it after completing Return to Karazhan: High Stress Hiatus. After picking up the Return to Karazhan: Clearing Out the Cobwebs quest I went back in without resetting and I came up three short for completion. It would be difficult to assess how many exactly I killed on the way to the portal but I wasn't careful where I ran so, in essence, if you're aware of what you're doing you'd have to be particularly unlucky not to be able to complete 40 spiders without resetting.

Edit 2: Made an adjustment as per suggestion by Gwiez.

Edit 3: Made a further adjustment as per suggestion by rngt.

Once this last quest is completed you can then do a Mythic run to summon Nightbane and he may drop [item=143556] for the item to port you to Karazhan. This only drops for those who have completed this quest chain.

This is the quickest and cleanest way to complete the quest chain that I've found so far. If anyone has a better method or notes any errors, please comment and I'll adjust the post.

If you forgot to return this quest inside the dungeon after defeating the boss, you can still meet Khadgar near the summoning stone in Deadwind pass:
/way Deadwind Pass 47.01 75.29 Archmage Khadgar