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