Here is the full list of all 23 Hidden: On the trail of the Ancients achievements.
Finish the game without using the hints system.
Completed the first part: "On the trail of the Ancients".
Find and protect the valuable object mentioned by Eneko.
Collect all findings.
Get rid of the creature.
Gathers information from the expedition , see what happened.
Read all books and notes.
Find and examine all books.
Find the device mentioned by Dr. Laura Garmendia.
Complete your mission at the boarding house.
Find the artifact which Adriano Scopelli mentions in his letters.
Find and collect information regarding Scopelli's diagram.
Examine every painting and picture in the boarding house.
Find and take a picture of the strange idol.
Find a way into what used to be Adriano Scopelli's room.
Fix the music box.
«I was in the front during the beginning of the Great War...»