The greatest part of writing characters like that is seeing their evolution and development. I had a character, a little similar to Isabeau, but she had her differences. She was the spy, not the assasin though :p Elora was the spoiled rotten neglected child of a rich family who killed her sister. She was so damaged when I started her out and she grew so so much. By the time I wrote her death, I cried. but it was perfect.