This is in the area where one has to jump down a few platforms, and there is a chest and ammo box below the platforms. A monster can also appear here. There is a gap between the wall and metal grilles to the right of the area exit, just up a flight of stairs and farther back. Saltzpyre is stuck in this gap and cannot jump out. Although Bardin is not inside the gap, he also cannot jump out.
Isn’t this close to the third tome?
Yes.