The Castle Fortress in Mortal Shell 2 is a highly complex special area. Once you obtain the Proxima shell, you can attempt to farm souls here. However, note that soul farming within the castle requires a certain level of skill; it's recommended to use the Warrior with high-damage Storm skills. During the process, you'll need to pull levers to open stone staircases. While this route doesn't allow for farming mechanical dogs, using the probe strategy makes boss fights extremely stable and safe.
How to Farm Souls in the Castle Fortress of Mortal Shell 2