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
The hows and whys of Joey
Reunite a family
Make a leap without falling once
Somebody's got to do it...
Find a secret room
Try to lie your way out of it
Complete the story
Free yourself
Blow on everyone you can find
Two becomes one
Keep clam and keep cool
She has plenty of time...
Gain access to an online game
Save your first ghost
Solve a puzzle together