This is getting exciting!
You know your castle just about as well as Adam Phillips knows his forest. Great atmosphere! The depth in background is very much above average. I praise your use of architectural details.
However, I cringe slightly at what in my humble opinion is the characters' poor planning in exploring the castle. What would be more foolhardy than sending just about everyone (or at least the bulk of the group) to rush into an unexplored, complex enemy structure with a non-combative scientist at the vanguard? This would lead to a whole bunch of bloodshed once the unseen enemy comes out. I nonetheless hope that's what happens, a massacre.
I'll definitely be watching the next chapter to find out.