Here is the full list of all 21 Another Sight achievements.
Complete the tubes Puzzle in "London Sewers"
Complete the world "London Underground"
Complete the world "London Sewer"
Complete the world "Monet's Garden"
Complete the world "A Cat's Dream"
Complete the world "Parisian Dream"
Complete the world "Laboratories"
Complete the world "Underworld Path"
Complete the world "Music Playing"
Complete the world "Underworld"
Complete the world "Node"
Unlock scene "The Only One"
Unlock scene "The Altruist"
Unlock scene "The Egoist"
Unlock all the Character Biographies
Unlock all the World Descriptions
Trap the guard outside the door in "Underworld Path"
As Kit, jump, climb and hide at least once
As the Cat, draw the attention of a guard by meowing
Complete the world "A Cat's Dream", dying less than 9 times
As Kit, draw the attention of a guard by turning on a generator