Into the Narrow Darkness
The passage continues ... deeper, darker, colder. There are gradual curves from time to time so any light that may have bled in is long past hidden.
Eventually, the party reaches an end to the tunnel, quite abruptly. There is a ... frame(?) here of long-corroded metal, squaring off the perimeter of the tunnel. It is somewhat larger than the average doorway. Shapes are etched (?) into it, partially obscured by dust and time. The space bounded by the frame is slightly dusty, but smooth. It seems to be comprised of an unfamiliar material. Perhaps a type of crystal? A polymer? Alloy? There are ... swirls (?) in the coloration, but no texture on the surface. It may be almost translucent or internally reflective, but that's difficult to tell.
On their walk, Alberic has sensed nothing active, nothing awake.