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 people of Dawnstar aren't sleeping well because they are all experiencing terrible nightmares. Erandur, a priest of Mara, wants the Dragonborn's help to destroy the Skull of Corruption, which will release Vaermina's hold on people's dreams.

Objectives

 * Follow Erandur to Nightcaller Temple.
 * Speak to Erandur.
 * Follow Erandur.
 * Follow Erandur to the Library.
 * Speak to Erandur.
 * Locate The Dreamstride.
 * Speak to Erandur.
 * 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 or allow Erandur to complete his ritual.
 * Take the Skull of Corruption. (Optional)

Walkthrough
This quest is given after visiting Dawnstar and speaking 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 the Dragonborn to travel with him to the Nightcaller Temple, which is just a short distance east of Dawnstar, to stop the nightmares. If pressed for details, he simply insists that the Dragonborn needs to trust him as a priest of Mara.

The entrance to Nightcaller Temple is the home of three frost trolls. Snow Bears, Snowy Sabre Cats, Ice Wraiths or Frostbite Spiders may be there instead, depending on the Dragonborn's level. At the entrance, Erandur warns about the dangers within. Priests and orcs battled, until a gas called the Miasma was released that put everyone (both priests and orcs) to sleep. He fears that, when the doors are opened, the gas will dissipate, and everyone will wake up and be hostile.

Once inside, the quest mainly requires the Dragonborn to follow Erandur. Erandur will cast a fire spell on the wall to create an opening. In the next room, Erandur points out the Skull of Corruption, and says that the inner sanctum must be entered. Following him down a curving set of steps leads to some leveled orcs waking up that will attack if given the chance, and a blue barrier. When the barrier is reached, Erandur reveals himself as a former priest of Vaermina who ran away during a long-ago attack on the temple by the orcs. He became a priest of Mara and now wishes to resolve loose ends in the Temple.

In order to pass through the barrier it will be necessary to go to the library to find the book The Dreamstride. There will be Vaermina Devotees to fight along the way and inside the library. Upon locating the book, Erandur states that there is a way to pass the barrier, but it requires Vaermina's Torpor, a potion that allows the user to travel by following another's dreams.

The next stop will be the laboratory, where Vaermina's Torpor is stored. There are some more invader Orcs and Vaermina Devotees that will need to be dealt with along the way. The Torpor is located on the shelf in the corner of the laboratory. It is next to three lit candles on the wall. When Vaermina's Torpor is located, Erandur instructs the Dragonborn to drink it and upon doing so, he or she becomes Casimir, a Vaermina Devotee during the Orc raid on the temple. Casimir is 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, the Dragonborn will find themselves on the other side of the barrier, where they must collect the Soul Gem powering the barrier. Erandur remarks about what happened, and then proceeds to the inner sanctum.

As the inner sanctum is approached, Veren and Thorek appear. They are the two Vaermina Devotees that told Casimir - the Dragonborn in the dream - to release the Miasma. After some short dialogue that reveals Erandur to be Casimir, they become hostile. After the battle, Erandur casts a spell to destroy the Skull of Corruption.

Here the choice is to kill Erandur as Vaermina commands and take the Skull of Corruption or let him complete his spell to destroy the Skull. If he lives, he can be a follower for no charge. However, this gives up the chance to acquire one of the Daedric artifacts, which are needed to obtain the Oblivion Walker achievement.

Notable items
See the Nightcaller Temple article for more details on available items.
 * The Skull of Corruption.
 * The Alchemy Skill book, Mannimarco, King of Worms, in the laboratory.
 * Unique book The Dreamstride.

Trivia

 * Both Orc and Dark Elf blood can be collected here for the quest "Discerning the Transmundane."
 * Using conjuration spells to resurrect the devotees and have them fight an Orc will generate unique dialogue.
 * Getting between Erandur and the wall when he uses flames against it, thus stopping the flames from hitting the wall, does not stop the passage from opening.
 * If Erandur is talked to while he is suspended midair in front of the Skull, it will break the spell holding him up and the normal dialogue options will appear. Exiting the dialogue will restore the spell and suspend him in the air again.
 * After going through the Dreamstride, all of the loot respawns on the dead enemies.
 * If the Dragonborn is wearing Miraak's Robes while in the Dreamstride, despite viewing the memories of another person, the tentacle explosion of the robes will still trigger in response to being hit by an attack.
 * If encumbered before entering the Dreamstride, the Dragonborn remains encumbered when in the Dreamstride with no way to remove items.
 * Followers cannot enter the Nightcaller Temple.
 * It is possible to get the achievement without the Skull of Corruption, thanks to a bug in the quest "Ill Met by Moonlight", where two daedric artifacts can be obtained.
 * It is possible to "talk" to some of the orcs if right next to them when they wake up, though they only spout general dialogue, and they will still attack afterwards.
 * Though the Miasma is supposed to degrade the minds of those under its effects, as seen with the cultists and orcs in the temple, Veren and Thorek appear not to have been affected as were the rest.
 * When in the Dreamstride, at the first corner of the hallway when running to release the Miasma, there can be seen a priest wearing hooded robes sitting on a bench and casually drinking from a tankard. However, this priest's body cannot be seen in the hallway after exiting the Dreamstride.
 * If Erandur is chosen over the Skull of Corruption, as a follower, he can be killed to fill other Daedric Princes quests, like Boethiah's call and the whispering door by using him as a friendly character.

Bugs
Ein lebendiger Albtraum Pesadilla viviente La fin du cauchemar Incubo ad occhi aperti Ходячий кошмар