Love
The main theme and also what drives the characters to act is love. A multitude of instances where love appears are present throughout the book. Love is what drives Jocelyn to sacrifice herself to keep her daughter safe and the reason why she didn’t run away when she had the chance. Because she knew that there was a chance that Clary may return home even after she told her not to, she stays behind even if that meant getting hurt and ended up being captured.
This type of love is also what keeps Jace, Alec and Isabelle together. Even if Jace is not related with them through blood, he loves them as his own family and regards them as his siblings.
Romantic love is also present in the book. Luke loves Jocelyn and even if he knows that she may not return his feelings, he stays with her and becomes Clary’s parental figure. When Jocelyn is kidnaped, he kills a pack leader so he gets her back. Because of his love for Jocelyn he takes care of Clary from afar and even if she believes that he abandoned her, he still sends werewolves to shadow her and take care of her is needed.
The relationship between Clary and Jace begins to become romantic but neither admits their feelings for one another. At the end of the book, Jace finds that he and Clary are brother and sister and he refuses to go with his father just to stay with her. Even if he refuses to see Jocelyn, he cares about Clary even if it is not sure if his feelings are romantic or not.
Identity
Throughout the book, many characters struggle to find out their identity. Clary finds that her world is not that simple and that her life is based on lies. She tries to discover who she is as a person and where she belongs in the Shadow World. In the beginning, she is afraid to give up her old life and holds on to her old self, refusing to believe that she is a part of a much bigger world.
Another person who struggles with accepting his feelings is Alec. He knows that if he were to come out as a homosexual he would be marginalized by the community and maybe even by his own family. He tries to hide his affection for Jace by using his status as his parabati as a shield for his feelings.
