Talk to the priest in the library about the Garden of Oblivion | Chapter V Memoria Guide

1 - to the main hall, 2 - to the council's room, 3 - to the observatory.

Click on the dark corner. There is a weird lamp with darkness, Sadja will take it. Go to the main hall.

1 - to the dragon hall, 2 - to the ore laboratory, 3 - to the guestroom, 4 - to the underground lake, 5 - to the library, 6 - outside.

From here you can go to the dragon hall, ore laboratory, guest room, underground lake, to the library and outside.

Go to the library and from here to the reading room. Talk with Ariarchos, he will give you a drawing.