Here is the full list of all 55 Silent Descent achievements.
Survived Section 1
Survived Section 2
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Survived Section 8
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Survived Section 15
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Survived Section 45
Acquire a Flashlight
Find and Read All Notes
Find and Collect All Hidden Picture Pieces
Complete the Letter Light-up Puzzle
Complete the Picture Light- up Puzzle
Solve the Flip Switch Puzzle
Solve the Letter Flip Puzzle
Survive a Chase Encounter
Find and Read Half of All Notes