The reality of Elder Gio's situation is a tad... confusing, but it can be summed up with the following statement: He stared into the abyss, and the abyss decided to spit in his face.
When Gio went looking for the Demon's Archive(Library of Nowhere) in the Jade Lake, he had actually found it after it had shimmered existence like a magic show. The smart thing to do in this moment would have been to head back to the surface and get back-up, or report a confirmation that the place existed.(Un)fortunately, Gio was a tad more greed than brains.
'If the Archive is as powerful as the legends say...then why should I bother sharing it with the others?'
Like a greedy little power gremlin, Gio beelined to the Library's entrance and attempted to abscond with its contents, at least that was the plan.
