After fighting Ketheric Thorm for the first time at the top of the Moonrise Towers, he will end up running away through a hole made by the Absolute in BG3. This whole leads into the Oubliette boss area in Baldur’s Gate 3 and you have to jump down that same area and chase Ketheric. However, once inside the Oubliette area, players get confused about where they should go as every corridor of this Mindflayer colony looks the same.
If you are stuck inside Baldur’s Gate 3 Oubliette, allow us to help you get to the other side.
How to get into the Oubliette in BG3
The right way to go into the Oubliette is through progressing the main story quest. You can access Oubliette once you defeat Ketheric Thorm. After his defeat, you will find a hole in one of the towers where you have fought Ketheric. Jump into the hole at the top of the Hollow Tower, and you will reach a Mind Flayer Colony. Inside the colony, you can also pick up the Chop! Chop! Chop! side quest.
If you kill Chop or convince him to give you the key, you can open a nearby cage to free an Intellect Devourer. This Intellect Devourer can then be used as a Familiar and summoned whenever you want.
How to cross the Baldur’s Gate 3 Oubliette and chase Ketheric Thorm
Once you enter The Mind Flayer Colony, you need to find Ketheric Thorm. The Colony is filled with many rooms. Explore the area. Ketheric can be found along the path between Bonedaughter and Necrotic Lab. There is an elevator that will take you to him.

Unfortunately, it is possible to get inside the Oubliette long before the boss fight. However, if that happens you will be stuck in there as there is nothing to do. Look for membrane walls that you can break down. Opening them up will allow you to leave the Oubliette in BG3 so you can return when the time is right.