It would be nice to have a codex in which as one goes exploring the game world can go registering information concerning all discovered.
Areas and places of interest:
When you discover a new area or place of interest that could be added to the codex with a representative image and a detailed description of its main features either geographical, of location or historical.
NPCs:
When you discover a new type of NPC that could be added to the codex with a representative picture and a description of its main features either historical as lifestyle, strengths and weaknesses to consider in the case of a possible future confrontation.
Plants, ores, logs:
When you discover a new type of these objects that could be added to the codex with a representative picture and a description of the possible geographical locations which would serve reference to locate efficiently.
The main source of enabling these additions to the codex would be active exploration by the player and how to activate it could be the payment of a sum in gold or crowns alternative option for registration fees.
Also you can set two ways to complete the codex recorded by a craftsman located in cities or personally buying registration materials which could be more economical but could have a daily limiting or time to complete the registration.
These are just some ideas of what the player could record in the codex, the possibilities are not limited.
What do you think?
Greetings!