Alec's sister, a beautiful and obnoxious Shadowhunter. She seems to have difficulty with romantic relationships, gravitating towards boys whom her parents disapprove of and quickly losing interest in them. Her favorite weapon is her whip which has caused the death of countless demons. Her attitude softens as the books continue, and it is revealed that she is very protective of both Alec and Jace, as well as being consumed with guilt when her little brother Max is killed. Isabelle is described as being stunningly beautiful, with long, charcoal-colored hair, shapely legs, and a slim waist. In the series, she has short flings with Simon and a fey knight called Meliorn.