Waking Nightmare

Background
"I've overheard two citizens of Dawnstar complaining about horrible nightmares. They seem to be relying on a priest of Mara named Erandur for assistance. Erandur has assured me he can end the nightmares, the source of which seems to be within Nightcaller Temple, a place of worship for Vaermina. I have agreed to assist him in this endeavor and we are now on our way."

- The Dragonborn

Objectives

 * Follow Erandur to Nightcaller Temple
 * Speak to Erandur
 * Follow Erandur
 * Speak to Erandur
 * Locate "The Dreamstride"
 * Follow Erandur to the laboratory
 * Locate Vaermina's Torpor
 * Drink Vaermina's Torpor
 * Release the Miasma
 * Disable the Magical Barrier
 * Speak to Erandur
 * Follow Erandur to the Skull of Corruption
 * Defeat Veren and Thorek
 * Speak to Erandur
 * Wait for Erandur to dispel the barrier
 * Murder Erandur (Optional)
 * Take the Skull of Corruption (Optional)

Walkthrough
This quest is given to you when you visit the Hold of Dawnstar and speak to Erandur, who is in the Windpeak Inn. All the townsfolk are suffering the same nightmares and Erandur knows how to get rid of them. He wants you to travel with him to Nightcaller Temple, which is just a short distance east of Dawnstar, to stop the nightmares.

Upon entering, Erandur will need to cast a spell upon the wall to proceed. In the next room you will face Invader Orcs, which vary in strength according to your level. When you reach the barrier, Erandur reveals himself as a former priest of Vaermina who ran away during a long-ago attack on the Temple by vengeful Orcs. He became a priest of Mara and now wishes to resolve loose ends in the Temple.

In order to pass through the barrier you will need to go to the Library to find the book The Dreamstride. Along the way and inside the Library, you will face Vaermina Devotees. Upon locating the book, Erandur informs you that there is a way to pass the barrier, but it requires Vaermina's Torpor, a potion that allows you to re-live the memories of another.

Your next stop will be the Laboratory, where Vaermina's Torpor should be stored. There are some more Invader Orcs and Vaermina Devotees that will need to be dealt with as you go along. When Vaermina's Torpor is located, Erandur instructs you to drink it and upon doing so, you become Casimir, a Vaermina Devotee during the Orc raid on the temple. You are instructed to release the Miasma to protect the Skull.

After releasing the Miasma by pulling a large ring on a chain on the wall just to the left of the barrier, you will find yourself on the other side of the barrier, where you must collect the Soul Gem powering the barrier. Erandur remarks about what happened, and then you proceed to the inner sanctum.

As you approach the inner sanctum, Veren and Thorek, the two Vaermina Devotees that told Casimir - the player in the dream - to release the Miasma come out and after some short dialogue revealing Erandur to be Casimir, they become hostile. After the battle, Erandur casts a spell to destroy the Skull of Corruption.

Here you can kill Erandur as Vaermina commands and take the Skull for yourself, or let him complete his spell to destroy the Skull. In the latter case, he can be hired as a companion for no charge. If you kill Erandur you get the following Daedric artifact: Skull of Corruption

Notable Loot

 * There is a large amount of Alchemy Ingredients (including 2 daedra hearts) that can be found in the Laboratory.
 * Most of the Vaermina Devotees carry Alchemy Ingredients as well.
 * In the Laboratory, there is the Skill Book Mannimarco, King of Worms.
 * There is an expert level chest behind a wooden door in the Library.
 * In the final room, there is a treasure chest on the right hand side of the stairs leading to the skull.
 * Outside, there is a chest on the backside of the tower (2nd tier) and a moonstore ore deposit on the left side, ground level.
 * The first room that you will enter in Nightcaller Temple has a novice level chest on the right of the magic sealed door of Vaermina.

Trivia

 * If you are trying to get both the Oblivion Walker achievement, and Erandur as a follower, save this artifact for last and create a save game prior to Erandur's ritual to destroy the staff. This is so that once the achievement is obtained through one save game, you can revert back to the older save file and have Erandur as a follower.


 * There is also moonstone ore at the back of "Nightcaller Temple".
 * There is an expert level chest behind a wooden door in the Library.
 * This is a great area to obtain Orc Blood for the quest, Discerning the Transmundane.

Bugs

 * There is a glitch associated with this quest where Erandur disappears when he enters Nightcaller Temple.
 * One possible solution is to speak to Erandur a second time outside the Temple before he manages to enter, then wait for 5 seconds before entering yourself. If nothing happens, Erandur might be back at the inn.
 * Another solution is to enter the temple before Erandur after you talk to him. He will then appear behind you and the quest may continue as normal.
 * On PC, if the above doesn't work, there is a fix which will reset the NPC bringing him back to you. This will reset his pathing and since the quest is mainly following and escorting him should clear up many bugs. In the console (accessed by hitting the key to the left of 1 and above Tab, which is labeled as ~ on most keyboards) enter, then  . Note that using the console will disable achievements until the game is restarted.
 * It may also be possible to fix the bug by waiting for 72-110 game hours, after which he might reappear at the inn. However, the glitch might reoccur when reentering Nightcaller Temple, so saving before either you or Erandur reenter is advisable
 * There is a bug, where Erandur does not move from the barrier or he can get stuck on the stairs after telling us that we should go to the library. Since the door of the library is closed and he has the key, the quest can't be continued.
 * On PC it can be solved by make the door of the library disappear (by console command) and go in. The next step of the quest will be initiated then. Pickpocketing the key probably also works. You can also push him up the stairs with Unrelenting Force shout. As soon as he is on top - the script will proceed.
 * On PC you can also use the "unlock" console command on the door to proceed with the quest.
 * This should work on Xbox, PC and PS3; Try punching Erandur a few times until he wants to fight you. Run up to the locked door then seathe your "weapon". He will stop fighting you and unlock the door.
 * This should work on Xbox, PC and PS3; You can also use your Unrelenting Force shout on Erandur twice to move him up the stairs. Then he will unlock the door.
 * It is also possible to stand very close to the barrier at which Erandur tends to stop moving. This will guide Erandur to his left after which he will avoid the barrier and continue walking without any blockages. (Confirmed on Xbox, not confirmed on PC and PS3.)
 * Due to Skyrims NPCs having an amusing sense of personal space, it's possible to make Erandur move up the staircase by simply standing too close to him. (Confirmed on PC and Xbox, not confirmed on PS3.)
 * It is also possible to get Erandur to continue by pushing him up the stairs using the Shield Charge perk from the blocking skill tree. (Confirmed on Xbox)
 * After deactivating the barrier and clearing the first 2 rooms, Erandur may run ahead and wait for the player in the final chamber to complete the quest. In doing so, he will trigger enemies on the way that will then look and wait for the player in the rooms he passes through. It is also possible for Erandur to disappear making the quest impossible to complete.
 * After waking up, the barrier must still be removed. If however the player waits for a significant length of time and kills all the enemies until the skull is reached, suddenly Erandur will run towards and past you, away from the skull only saying you've got to hurry. He'll eventually disappear and after removing the barrier another Erandur will still follow you, triggering the final battle.
 * Sometimes, the player can talk to the enemies before they awaken. They will say something, then "awaken" in a hostile state.
 * After the last fight, just before reaching the skull of corruption, Erandur will offer no dialog options.
 * It is possible that reseting his location to the player will resolve this issue (open the console and type  and then  ). Exiting and re-entering the temple fixes this bug (Xbox 360 confirmed).
 * For PS3, try leaving the temple and returning to Erandur, dialogue should return then.
 * Upon entering the library, if you pick up the book "The Dreamstride" before prompted to by Erandur, it may prevent him from prompting you, making it impossible to continue with the quest.
 * The same may also apply to collecting "Vaermina's Torpor". (Untested).
 * There is a bug on the (XBox360, PC) where he will freeze on the stairs to the library making it impossible to complete the quest. However, if you attack him and keep hitting him until his body is up the stairs he will get unstuck and be hostile. At this point exit and reenter the building and it will reset his quest action so he will go and unlock the library. Maybe this would work for the other bugs where he gets stuck on something. Until the end of the quest he is indestructible so it is safe to hit him. Another way of moving him is to walk into him and slowely he will move up the stairs.