What about the Tomes? I think they have something to do with some secret.
When you look at the 4 times they say this :

07:47 You see a green tome.
It weighs 19.00 oz.
It is a volume of The Mystic Secrets of Tibia.

07:47 You see a grey tome.
It weighs 19.00 oz.
It is a volume of The Mystic Secrets of Tibia.

07:47 You see a blue tome.
It weighs 19.00 oz.
It is a volume of The Mystic Secrets of Tibia.

07:48 You see a red tome.
It weighs 19.00 oz.
It is a volume of The Mystic Secrets of Tibia.

Now you know they are all empty & you cannot write in them.
They say "It is a volume of The Mystic Secrets of Tibia".
I think you may need an NPC to read them too you, or learn some kind of magic so you can make the texts appear, than it will give some kind of hint towards some secrets.