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