Contract: Doors Slamming Shut - Novigrad
Quest Giver: Hierarch Square Notice Board Gildorf Notice Board
Other Requirements: N/A
This quest is started by visiting either the Hierarch Square or Gildorf Notice Board in Novigrad. If you try to speak with the NPC above without visiting either Notice Board, he will not give you this quest.
When you're ready to begin this quest speak with Count Kury Dysart who is found on the second floor of the Kingfisher. He'll update your quest and send you out to the Moldavie Residence to the east of Novigrad out in Velen. Investigate the house, most importantly check the downstairs where you will find a draft coming through a cracked wall. Aard it open to find a secret passage.
In the Elven Ruins you'll find a journal and a root on a table near a locked door. You'll conclude here that it's an Earth Elemental causing the disturbance in the house. To open the door that leads to him you'll want to jump into the water and head to the eastern end of the room, there will be a lever on the wall to pull.
The fight with Therazane will be pretty tricky - assuming you don't want to get Kurt killed. With this quest, if you destroy the wooden supports holding up the stone in the same room as Therazane (it's very easy to destroy them) then Kurt will die when inspecting the house at a later time since the ceiling will collapse on him.
As far as I know Kurt dying doesn't change any future quests and it doesn't alter your reward at all, it's just a small story element. When you're ready to fight Therazane, to awaken him/remove the blue shield all you have to do is Aard the crystal that is behind him.
Therazane Weaknesses: Dimeritium Bomb & Elementa Oil