Here is the full list of all 34 Demonheart achievements.
Finish Chapter 5.
Max out both Good and Tactful points.
Finish Chapter 4.
Read all the entries of Rivera's journal.
Finish Chapter 3.
Finish Chapter 2.
Finish Chapter 1.
Read the book about demonspawn in Chapter 1.
Max out both Evil and Tactful points.
Max out both Good and Defiant points.
Max out both Evil and Defiant points.
Decipher all the messages in Chapter 1.
Examine Mr. Edgardo after the dinner with Orchid.
Molest the demonspawn.
Decipher the message in Chapter 2.
Kill Mark.
Decipher all the messages in Chapter 3.
Ask the demonspawn as many questions as you can.
Kiss Sir Brash.
Decipher the message in Chapter 4.
Finish the game as Good Bright and as Evil Bright.
Decipher the whole message in Chapter 5.
Kiss Ari.