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