You can find the Doctor in the 'Black House' in the northeast. A nurse will open it to tell you to stop.

You can use the barrel east of the house to teleport a teleportation pyramid into the cellar. You can just enter the house when you play Lohse. You will earn 19,400XP and your journal will update. Once you have killed one of them, an Elven messenger will appear, clapping and bidding your party to visit Doctor Daeva at his house. You can kill either Isbeil in the quest, 'The Secrets of the Dwarves', or you can kill Lord Linder Kemm in the quest, ' The Vault of Linder Kemm'. There are now several ways to progress this quest in Arx. The plant encounter will give you 193,950XP. Note, there is also a separate encounter at the Kemm's Garden with some plants which were grown from 'peculiar seeds' that Doctor sent to Lady Kemm intended for Lord Kemm. It is recommended to do the School, Consulate and Gardens encounters before the other main quests, especially before advancing into the Isbeil or Vault quests. On DE, the three encounters will not trigger if you have pursued the other quest lines, locking you out of this XP. Killing all 4 of them will yield you 599,400XP (229,700 XP in DE Edition). They may flee but but you will encounter them again at the Lizard Consulate and Kemm's Garden. On the other hand, if you killed the Advocate you will be ambushed at the same place by said citizens, revealing themselves as Nemesis demons.

Outside the schoolhouse in Arx, a distressed citizen may tell you that the doctor thanks you for serving him back at Bloodmoon island, if you helped the Advocate. Investigate the wedding site in Arx, which is also related to the quest, ' The Secrets of the Dwarves', and you will learn that the doctor was the one who sent the explosive wedding cake to the dwarves with the intent to kill at least someone named Isbeil, based on the note left behind. If you speak with Jahan, he will tell you that the good doctor is the demon and is currently hiding in Arx. The name of the demon can be learned from the ancestor tree spirit at Bloodmoon island.

Snuff out the candles to weaken The Doctor (optional).

Learn the name of The Doctor from the Spirit of Ancestor Tree.

Doctor Daeva is actually the powerful demon, Adramahlikh. Doctor's Orders is a Quest in Divinity: Original Sin II.

Doctors orders