Here is the full list of all 14 Within Skerry achievements.
Complete Within Skerry by achieving the third ending
Locate all notes
Unlock all vault spinners
Unlock the little white marble vault
Complete Within Skerry by achieving the second ending
Get off the kitchen counter!
Locate the holy cross to help fend off evil
Snap 15 photos of paranormal activities
Complete any ending of Within Skerry in 25 minutes or less
Escape the enemy trying to capture you
Snap 10 photos of paranormal activities
Complete Within Skerry by achieving the first ending
Captured by the enemy running after you
Collect all cassettes