Celia was sitting on the floor when Percy returned to his cabin that summer.
Before he had time to process that a) There was a girl in his cabin and b) there was now a second bunk on the opposite side of the room from his, she had risen and stuck a hand out for him to shake.
"Celia Travers," she announced calmly, "It looks like we're roommates now!"
This was new. Percy hadn't known he had any demigod siblings until now. He looked closer at Celia. Her eyes, though the exact same shade of green as his own, were almond-shaped and intelligent looking. She looked about his age, but was almost a head shorter, and lean. Percy shook her hand.
Celia's mouth twitched up on one side. "The look on your face," she made a picture frame with her fingers and closed one eye as if to line it up with his head, "Priceless." She gingerly sat back down on the floor, and Percy followed her. He didn't really know what to do right now. This was totally uncharted territory. He wanted to know everything about this short, slight, girl who had just waltzed into his life.
"How were you injured?" Percy blurted.
His new roommate grimaced, "That obvious, huh? My track coach decided to try to run me through with my pole." As if that made anything clearer. Seeing the confused look on Percy's face, Celia elaborated. " Pole Vault pole. Sorry. Anyway, my coach was actually an Ogre, and he tried to kill me at the end of the season. I would've thought he would use something that was actually sharp, like a javelin, or something heavy like shot put, but I guess he wasn't that bright. He managed to break my ribs. It really hurt and I accidentally broke a nearby fire hydrant, and then I used my mad water-bending skills to destroy my coach. Next question."
Percy stared at her. Celia winced and said "I know you're curious! And your schedule arrived with mine, so I know you don't have to go anywhere until dinner, and I want to get to know you. Anyway, can we sit on a bed or something?"
They moved to Celia's bed. Percy pulled a stool out from under his bed and carried it over. While Celia was getting into a comfortable position Percy took the opportunity to observe her a little more. Her hair was really long, her braid fell to the middle of her back, and in both of her exposed ears he saw four piercings. Each one had a tiny golden stud gleaming in it. She was wearing the standard issue Camp Half-Blood t-shirt and a pair of cargo shorts. When she had finally propped herself up in a way she liked, he noticed that she was fiddling with a small smooth stone in her lap.
"Now," Celia interrupted his silent observations, "We know each others names, and I know your schedule, and you know my latest being discovered by monsters story. Where do we go from here?"
"How old are you?" Percy asked.
"Almost 16," Celia said.
"Whatever," she said, "I only have like a week. Next?"
"Okay, how did you survive until 'almost 16' before having a major attack and satyrs finding you and bringing you to camp."
"Living in a mobile home and being home schooled until High School. Next?"
The questions went on until dinner. By that time, Percy knew that Celia had lived with her mother (who was 100% Indonesian, but born in Pittsburgh and worked as a travel writer) her whole life, and had been told that her father went MIA in a top secret submarine accident so she couldn't talk about him. In those days if she saw anything through the mist, she would draw it. Celia had been afraid that she was going insane, because her mother always looked worried when she showed her mother these drawings. So she stopped showing her mother. The night she turned 13, her room lit up in green, and she had strange dreams every night from then on. Life went on like this until she turned 14 and her mom became convinced that she needed to go to a public school in Kansas, and she started running, was good at it, and had to kill her track coach.
Percy had given Celia the Cliffs Notes version of his life, and promised to introduce her to his friends later that night. Then they walked to the dining pavilion together, and Percy realised that for the first time since the Argo II, he wouldn't have to eat alone.