Andor's Trail

I'm not sure if this has been covered in another thread, but I'm experiencing an issue where I can't get close to the formidable demon lurking in the Flagstone prison basement. Initially, I completed the prison quest on a lower level while using version 6.8. Now, at level 16 and on the alpha 6.10 version, I went back to Flagstone seeking extra XP. That's when I noticed the previously locked center cell in the basement was open, revealing a hole in the wall. However, every attempt to approach the demon is thwarted by an invisible force repelling me. I thought the warden's necklace might be the key, but there seems to be no way to use it in this context. Am I overlooking something?

Did you talk to the guard outside the prison again? He might have an idea.
But maybe it's not working. From your description it's new content in a higher release

Version 6.10? Problems in Flagstone? Are you using the BOP version?

Did you manage to get the warden's necklace?
If so, it's not the job of the outside world to answer your questions.