A Small Problem Talk to Varric in The Hanged Man and agree to aid him to start the quest 'Haunted' .
Head on over to Hightown at night and visit Bartrand's Estate. Loot the crate at the entrance then continue west. Head north to the upper section of the Estate and enter the eastern room. Check the crate after the scene and start backtracking until a door is open to the middle area. Head up the steps and check the left room for a chest - complex . Enter the middle room to start a scene and ultimately a boss fight. The Ethereal Golem uses a few attacks that are like the Ancient Rock Wraith. After taking 1/3 of its HP it will summon Shades to attack. It will do this again after taking another 1/3 of its HP, the final time it returns will be its last and the Ethereal Golem will now be red. Loot it for the Rock Band and afterwards a scene occurs.
After the battle you get a choice to keep a part of the idol or give it to Varric. Keeping it means you must return to Sandal who will make a Primeval Lyrium Rune while letting Varric have it results in 3 rune slots for Bianca. Go back up the steps and into the room on the right for a chest - master and a Ledger .
Head back to The Hanged Man to speak with Varric. This will close out the chain with Varric.