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".
Collect all findings.
Find and protect the valuable object mentioned by Eneko.
Get rid of the creature.
Find the device mentioned by Dr. Laura Garmendia.
Find and examine all books.
Read all books and notes.
Gathers information from the expedition , see what happened.
Complete your mission at the boarding house.
Find and collect information regarding Scopelli's diagram.
Find and take a picture of the strange idol.
Find the artifact which Adriano Scopelli mentions in his letters.
Find a way into what used to be Adriano Scopelli's room.
Fix the music box.
Examine every painting and picture in the boarding house.
«I was in the front during the beginning of the Great War...»