The Thing Inside

Template:Pagename nd is an origin quest of Lohse in Divinity: Original Sin 2.

Quick walkthrough

Find the demonologist. When you find him he gives you two quests. One is to assassinate the Advocate and the other one is to acquire the Archdemons name. The name can be acquired by talking to the mothertree in middle of the island. The tree will respond in alien language for the first time. To be able to get the name you have to find the name of the tree first in the archives which are on northern part of Bloodmoon Island and then speak to her again.
Assasinate the Advocate. During this quest you have to kill the Advocate (Adramahlihk will not be pleased by this and will send his lackeys after you once you are in Arx).
Report back to Jahan. Once you have killed the Advocate and acquired the Archdemons name he will try to exorcise the demon from Lohse. This attempt is unsuccessful and after this he goes to Lady Vengeance. He can also teach you how to harness Source but through purging his demon prisoners.

Journey to the city of Arx. The origin quest for Lohse states that she must now travel to Arx to progress it.
Speak to Malady in Arx. After the player arrives in Arx, Malady will tell Lohse that she has a plan on how to deal with Archdemon and will say that you have to meet her before his house.
Travel to Adramahlihk's home plane. During this quest Lohse has to douse all candles which contain the persons soul (this will result in their permanent death). You can leave the dimension or refuse to snuff out the candles but if the player does so they will have to face Adramahlihk in full strength (He is one of the hardest bosses in game)
Face the demon. Face Adramahlihk. - Face Adramahlihk. If you fight him you have to defeat him in three rounds because if the player doesn't do so he will permanently possess Lohse (if Lohse is your main character you get Game Over).

- If you side with him you will get "Demon Ending" and he will kill all characters which were not in your party (including Dallis and Lucian if they survived and the player sided with them)