Ancient pages are items which are sometimes obtained when rummaging barbarian skeletons or as monster drops in the Ancient Cavern. Duplicate pages may still be obtained before completion of My notes if rummaging skeletons. They are part of the book My notes. There are 26 different pages. Finding all the notes is one of the requirements for the Trimmed Completionist cape and Master quest cape.
Our best guess is that some sort of heat generation process is occurring in the tunnels we have scryed, though the denizens are proving quite a hindrance to our free travel. Research was never this dangerous for my teachers.