Here is the full list of all 18 Blackwell Epiphany achievements.
Create no more than 450 footprints
Finish the game in commentary mode (from the first screen till the last)
Learn a long kept secret
Blow on everyone you can find
Make a leap without falling once
Somebody's got to do it...
Find a secret room
Keep clam and keep cool
Try to lie your way out of it
Complete the story
Free yourself
The hows and whys of Joey
Two becomes one
Reunite a family
She has plenty of time...
Gain access to an online game
Save your first ghost
Solve a puzzle together