Night Terrors

Night Terrors is a secondary quest in Dragon Age II.

Acquisition

You can acquire this quest from a letter in your home. It is preceded by "Wayward Son". This one will be available after completing the Deep Roads Excursion portion of the game.

Walkthrough

Before Entering the Fade

After your conversation between Keeper Marethari and Arianni, the Keeper will talk to you in person, asking you to kill Feynriel should he turn into an abomination. If you answer "I understand", Anders: rivalry (+5), Merrill: rivalry (+10), Sebastian: friendship (+10) (Only if Merrill is also in the party). The other option "I can't do that", Anders: friendship (+5), Merill: friendship (+5), Sebastian: rivalry (+10).

Torpor (Sloth Demon)

The first demon can be found immediately upon entering the front door. The demon will offer you a deal if you agree to hand Feynriel over. If you take the offer he'll offer you Power, Knowledge or Magic. If you take the offer and Anders is in the Party, Justice will object and you will have to fight Anders ( Anders: rivalry (+15) Fenris: rivalry (+15) Aveline: rivalry (+15) Merrill: friendship (+5) (Winning fights with party members in the Fade only causes them to leave your party temporarily during you stay in the Fade, not permanently as is the case in Dragon Age: Origins/Awakening)

If Hawke rejects the offer, Torpor must be defeated ( Aveline: friendship (+10), Anders: friendship (+10), Fenris: friendship (+5), Merrill: rivalry (+5)). Hawke will now be able to go up one of two stairwells where two doors regarding Feynriel await. Once you get through the visions simply pick your choices to make Feynriel aware of the demon being present. You will also encounter a rage demon where Torpor was located previously once you've completed a room.

Caress (Desire Demon)

Found within the door labeled "Feynriel's Desires"

The following party members will betray Hawke when tempted by this demon:

Aveline - Tempted by getting back her deceased husband, Ser Wesley.
Isabela - Tempted by the offer of a new ship and crew.

Wryme (Pride Demon)

Found within the door labeled "Feynriel's Pride"

The following party members will betray Hawke when tempted by this demon:

Fenris - Tempted by being given power enough to be an equal to the Tevinter mages.
Merrill - Tempted by the offer of power enough to save and protect her people.
Varric - Tempted by the offer of power to get back at his brother, Bartrand, for his betrayal in the Deep Roads.

If either Caress or Wryme succeed in tempting a party member, Hawke will have to fight the demon along with the tempted party member. Once the companion is defeated, they will leave Hawke's party and wake up from the fade. Anders will never be tempted as Justice keeps him safe here. Sebastian will refuse to even enter the Fade as a man of the faith.

It appears that the party members listed above will always betray Hawke, regardless of friendship/rivalry points or the resolution of issues related to their temptation. For example, even if Varric's friend meter is maxed out and he has confronted Bartrand during the relevant companion quest, he will still betray Hawke when tempted by Wryme. Likewise, Aveline will still betray Hawke when tempted by Caress, even if she has a full friend meter and has begun a relationship with Donnic in "The Long Road" quest.

On the other hand, some characters will more likely betray you. If both Isabela and Aveline are in your party, Isabela will receive the demon's offer. Same thing if both Fenris and Varric are in your party, where Fenris will get the offer.

Hint: Check out the side chambers for a codex entry.

Feynriel

Once all demons are defeated, head back out to where Torpor was to encounter Feynriel and decide his fate.

Ending Outcomes

There are three possible outcomes for Feynriel for this quest:

1. Make a deal with Torpor the Sloth demon and pick your reward. You must convince Feynriel he is in a dream or the Sloth demon will say his mind is useless and attack you. - Feynriel is considered dead when quest is complete.

2. You save Feynriel. With Hawke's refusal to kill him and encouragement, Feynriel will seek out the mages in Tevinter for further knowledge on how to handle his abilities. His mother won't like not saying goodbye, but understands. The Keeper will reward you with the Tome of the Slumbering Elders. Pick the options "You will not die" and "I will not kill you." If you didn't tell Feynriel of the demon and he figures out for himself, Feynriel will be more confident in his abilities and will not ask for you to kill him.

3. Make Feynriel a tranquil at his behest by killing him with the fade by selecting the option at any point "As you wish.". His mother will be devastated. Even if you didn't tell Feynriel of the demon and he figures it out for himself, you still have the option to make Feynriel tranquil. Choose "I cannot let you go."

Betrayals by companions will result in quests for each betraying companion. Depending on Hawke's dialogue choices it can lead to friendship or rivalry points.

Aveline - Doubts that Linger
Fenris - Fenris Night Terrors
Isabela - Isabela's Apology
Merrill - Merrill, An Apology
Varric - Varric's Apology
Anders - Anders in the Fade

Puzzles

The flying book in the first room can be read. As it will always stop at roughly the same places simply wait for it and pause to click on it. You will get +1 attribute point.
East of the first room are 7 barrels that can be moved by clicking on them. If you can get all four large barrels on the floor and the three smaller ones above them within the move-limit you get another +1 attribute point. You only have a limited number of moves to make. In order to successfully complete this puzzle, you must first move the top two big barrels on the right, exposing the left-middle small barrel. Move this barrel up, and the big barrel on the left down, move all the small barrels up and move the big barrels down and left.
The second barrel puzzle is in the next room to the east. This time you have to get all four red barrels into the middle of the 10 barrels to get another +2 attribute points. This puzzle is much easier than the previous, simply move the left/right-middle barrels up, rotate the barrels to get the red on the bottom, move the bottom red barrel up and the rotated red barrel under it.

Rewards

4 attribute points:
1. 1 for reading the Book in the first room
2. 1 for solving the first barrel puzzle
3. 2 for solving the second barrel puzzle
If Hawke sides with the demon:
1. 6 attribute points if Hawke chooses "Power"
2. 1 talent/spell point if Hawke chooses "Knowledge"
3. 2 unique runes that offer magic resistance if Hawke chooses "Magic"
If Hawke does not side with the demon:
1. Tome of the Slumbering Elders (loot item)

Notes

It's possible for companions at full (locked) friendship to still side with the demons, regardless of dialogue choices (this is intentional).
As the Fade is naturally home to Justice, he is in control of Anders while there. He cannot be tempted by demons but he will turn on you if you decide to side with the sloth demon and will try to stop you. You can earn friendship points that count towards Anders, but you will be dealing with Justice.
Taking Merrill into the Fade can lead to some heavy rivalry points with Merrill. She will always gain rivalry points when talking with Torpor—the sloth demon—and does not take kindly to instantly refusing the demons or scolding her when she is tempted by Wryme—the pride demon.
- Merrill: friendship (+5) is possible by 'allowing' Merrill to be tempted by Wryme via the middle "Humorous" option, though she will still defect. Similarly, wry responses can get even Isabela: friendship (+5) though she fights against you. If you have both Merrill and Anders in the party when talking to Torpor and continue the discussion with Torpor until Anders forces you to either reject its offer or fight him, rejecting the offer at this point will not loose or gain you any favor with Merrill, but will gain Anders: friendship (+10).
When Keeper Marethari arrives and takes you aside to give you an additional warning, answering "I understand" will gain you Merrill: rivalry (+10) and Anders: rivalry (+5)). Responding "I can't do that" will give you friendship points with both. ( Merrill, Anders: friendship (+5))
Sebastian: rivalry (+10) if he is in the party when you speak with Arianni in regards to the quest, stating it was what caused the fall of the Golden City by Tevinter mages. He will also refuse to be in the party to enter the Fade, stating it's no place for a man of the faith.
The DLC Mabari hound can be very useful here as both he and Anders can't be tempted. However, when gearing up for the Pride demon fight, wait to summon the dog once the fight is initiated or he might be locked out behind the door.
The Attribute points earned by the puzzles in this area are earned by the active, controlled party member, regardless of whether or not this character is Hawke.
If you take two companions that can be tempted by the same demon, only one will turn.
As a side note, if you turn off the tempted character's tactics, and add one with Self/Any/Wait, they will just stand there for the whole fight making things much more manageable, especially if your allies are very strong. You will need to set the tactics before you enter the room, since once the battle starts, they are no longer part of your party, and thus their tactics cannot be chosen.
If you visit Sundermount before starting this quest you may encounter Templars demanding a group of Dalish hand over Feynriel (if you sent Feynriel to the Dalish (or let him choose) at the conclusion of Wayward Son). During the conversation you can side with the Dalish in a fight against the Templars, side with the Templars in a fight against the Dalish, or simply leave the conversation. Siding with either side results in Isabela: rivalry (+5) while simply leaving results in Isabela: friendship (+5). It is also possible to convince the Templars to leave without violence.
Demon always tempts the same character on multiple reloads. If the fight with this particular character is too hard, use Maker's Sigh on them before entering the room. They'll be forced to fight stripped of all their abilities and attribute points, which will make this encounter more managable.
When Isabela is tempted with the offer of a ship, she will respond to the demon by saying "I like big boats, I cannot lie." This is a possible reference to the rap song "Baby Got Back." If Hawke has taken on the sarcastic voice type, he will question her about this line during Isabela's Apology.