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