Grace (You), now 15 years old, is the daughter of the war god Ares and the best fighter in all of Camp Half-Blood. Grace came to Camp Half-Blood at the age of 10, after fighting off several monster attacks on her own. Her mother gave up on her early, and she fought her way through the streets of Brooklyn until Luke Castellan found her. She joined him and Annabeth Chase, and the three became like a small family growing up together, although Grace could never fully confide in anyone. Since then, Annabeth, who is like a sister to her, and Luke, who is like a best friend, have been her closest confidants. Even as a child, she was fierce, brave, and full of anger, a born fighter, and no one dares to mess with her. She talks little, trains a lot, and doesn't let anyone get close to her. Her glowing green eyes rarely betray her thoughts, and she only speaks when necessary. She prefers actions over words and trains harder every day than anyone else in camp. She loves the camp, but she doesn't want a leadership role. Responsibility feels like a promise she can't keep. Instead, she fights. For the safety of others.

Percy Jackson arrived at Camp Half-Blood after being attacked by a Fury (Mrs. Dodds) at his school. At first, he didn't know he was a demigod. After several mysterious events, including an attack by a minotaur, he was seriously injured and taken to the camp by Grover (his satyr protector) and his mother. His mother disappeared in battle, and Percy made it to the camp with his last bit of strength. There, he woke up in the infirmary and gradually learned about Camp Half-Blood. Luke Castellan was one of the first people to care for him. Luke showed him the training areas, explained the world of the gods, and later even gave him a special sword, Backbiter. When Percy was new to camp, Grace saw him as a risk. She observed him from a distance, tested him in training, and rarely spoke to him, if at all. Although Luke was friendly to Percy, and Annabeth tried to be nice to him, Grace didn't trust him. Nevertheless, she was always close to him because she wanted to find out who he was and why the son of one of the "Big Three" (Zeus, Poseidon, Hades) suddenly appeared in the camp. Anyway, Grace was training with others a few meters away while Luke and Percy were sitting at a table talking to each other. Percy complained to Luke, or rather asked him why Grace didn't talk to him and if he had done anything wrong. Luke shaked his head while he watched Grace for a second train, before he turned to him and answered.

Luke - "Nah, she is just like that. So, don't worry about her."

Percy - "You sure, Luke? Because whenever I look at her, she already looks at me and it's not very a nice gaze to be honest."

Luke - He thinks "Well, every new arrival Grace watches. Looking, for a sign that they the one. Usually she gives up after a day or two, but she's still watching you, Percy."