Haunted

Haunted is an Act 3 companion quest for Varric in Dragon Age II.

Acquisition

This quest can be obtained by speaking to Varric in The Hanged Man after completing On The Loose and A Small Problem.

Walkthrough

This section contains spoilers for:
Dragon Age II.

Go to Hightown and enter Bartrand's Estate.

Note: The quest description says you must go at night but you can access the estate and the quest during the day as well.

Make your way through the house until you can go upstairs and into the center room. After a cut scene you will be faced with an Ethereal golem which will provide 2050 XP upon its defeat. It will disappear after a short time and spawn several shades which you will have to defeat before he becomes attackable again. When the golem attacks, the floating paraphernalia will intermittently strike nearby team members, doing little damage but knocking them back and potentially interrupting moves.

After the battle you find a piece of the idol. You will then have an option to let Varric keep it or get rid of it.

If you let him keep it, this will give him three extra rune slots on Bianca, and will result in Varric: friendship (+10), Anders: rivalry (+5), Sebastian: rivalry (+10).
If you make him get rid of it, you'll be able to give it to Sandal who will make a Primeval Lyrium Rune out of it. The latter option will result in Varric: rivalry (+10), Anders: friendship (+5), Sebastian: friendship (+10).

Also after the battle, the room at the top of the stairs on the right, which was previously locked, will unlock. Visit it to loot a master difficulty chest and examine a ledger near the bed which will trigger a cutscene with Varric.

Rewards

2050 XP (for the fight) and 1200 XP (quest completion)
Rock Band looted from the Ethereal golem
Acquisition of the quests Closure and An Anniversary

There are two possible outcomes:

Varric's armor will change names to Varric's Armored Leather Duster, and Bianca will be upgraded with 3 additional rune slots (4 total) if Hawke allows him to keep the shard. You will also receive the Codex entry: Bianca.
Sandal will make a Primeval Lyrium Rune from the shard, which increases attack speed (varies by weapon strength).

Trivia

The picture on the ground in the room where Varric Tethras talks about Bartrand and the broken plate is the same image as is used for the Kindly Knight in Dragon Age: The Last Court.

Bugs

When the Ethereal golem shows up, the journal says to defeat the Rock wraith.