Content Warning: This section of the guide describes and discusses the source text’s treatment of alcohol, substance, and gambling addictions.

Theresa Gray, the protagonist, is an orphaned American teenager who discovers she is a warlock, born of a union between her human mother and a demon father. She has the power to take on the appearances, mannerisms, and thoughts of others. At the start of the novel, the narrative focuses on Tessa’s love for her brother, Nate, and her love of reading. Tessa is tall and fair, with “smooth brown hair and steady gray eyes” (17). Her goal at the beginning is to survive the Dark Sisters’ training and then escape with her missing brother, returning to a simple life where Nate will provide for her until she is married. Nate is her only family: “without him, she was completely alone in the world” (17).

Her goals and identity change when she discovers her power and her origins in the Shadow World of warlocks, demons, Shadowhunters, vampires, and werewolves. Tessa struggles to accept her non-human identity but ultimately embraces her power and her place in the Shadow World by the novel’s end. Her perception of family changes from seeing Nate as her only family to seeing the Shadowhunters as her found family.