Gannon [and anyone that follows him]: Directly to the left of the old temple is a gigantic column of stone; presumably it holds up the roof of the cavern to some degree or had at one point. Ahead of that and to your left (at a heading of about 45-degrees left from where you are standing right now) is a mostly intact building.
The building is solid and, as far as you can tell, completely intact. A set of double doors, made of adamantine and bearing the same spiderwebbed seal that adorns the cover of Geldem's journal, dominate the building's front.
Flawed checks if the symbol also contains those mithral veins as the journal and the seal. If so, it pushes the journal against the seal here as well, emboldened by the success at the first seal.