Here is the full list of all 27 The Sand Man achievements.
Try speaking to every sleeping person
David makes his appearance
Find Anne within 3 minutes
Escape the mall in a cardboard box
Escape the dragon's wrath
Find all suspicious events in various locations
Get Game Over from being pulled into the swamp by Nixie
Received a coin from the toothfairy
Get Game Over by failing to escape the Sandman
Get Game Over by eating the Sandman's cooking
Drop the Sandman down the trap-door
Give the unicorn the fake pink gem
Give the unicorn the real pink gem
Receive the pink gem back from the unicorn
Capture all the fairies of light
Speak to the unicorn beaten by the Sandman
Look at Sophie's photo
Read all entries of the Sandman's diary
Make a mistake when preparing the Sleeping Sand
Prepare the Sleeping Sand without making any errors
Get caught in the trap after obtaining the fire emerald
Get Bad Ending 1
Get Bad Ending 2
Get Bad Ending 3
Get the Good Ending 1
Get Bad Ending 4
Get the Good Ending 2