Here is the full list of all 20 Ghost of a Tale achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Play all songs during the course of the game.
Reach the end of the game.
Complete the game without getting hit by an enemy.
Complete the game without ever eating to regain energy.
Complete the game without alerting any guards.
Finish every secondary quest.
Set fire to all inflammable items in Dwindling Heights.
Learn all skills in the adventure.
Complete all of Gusto and Fatale's quests.
Complete the full set of Duinlan's armour.
Unlock forty-five footnotes.
Rid Dwindling Heights of all spiders.
Discover the name of every possible character in Dwindling Heights.
Reach the desolate shore.
Steal all of the Rat Guards' handkerchiefs.
Open all window shutters.
Discover Duinlan’s tomb.
Gather fifty-five mushrooms.
Reach the highest point in the highest tower.
Escape from Tilo’s cell.