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