|“||I can't even qualify for the Olympics until I'm sixteen!||”|
–Kayla in The Hidden Oracle
Kayla is among the campers that go to New York City and fight for the Olympians. She and her half-brother, Austin, set traps along the Brooklyn Bridge with their half-brother, Michael Yew, directing them.
Kayla survives the battle and is commanded by the new cabin counselor, Will Solace, to look for Michael Yew. Michael's body is never found (though he is later revealed to have died), as this seems to be the general opinion at the memorial ceremony. Percy Jackson only sees his bow and presumes that he had fallen into the river below the Williamsburg Bridge.
Kayla, along with Austin, visit Apollo when he is brought to Camp Half-Blood. After learning that their father became a mortal, Kayla worries if the skills and powers they'd inherited from him are going to disappear. She then asks if they themselves are going to be un-born, her father assures her that it would not happen.
The next day she tells Apollo to keep practicing and his archery skills will improve. She was shocked when he swore on the Styx to not play music or practice archery until he was a god again. They stopped Sherman Yang from going into the forest. She was paired with Austin for the three legged death race, but the two were taken hostage by Nero. She was freed by Austin and rode the queen Myrmeke with her father, she rode in the flying chariot with Apollo and Austin to take down Nero's automation Colossus Neronis.
Apollo mentioned that Kayla told him to maintain his equipment while traveling. When her immortal father is aiming for the lever on the train tracks, he remembers what she had told him about patents.
After escaping the Strix, Apollo wonders how his daughter is doing at camp.
Kayla has short ginger hair dyed with a shock of bright green and blue bell eyes. She has freckles covering her skin.
Kayla is shown to be kind, as she tried to calm her immortal father when he was turned mortal. She is also driven, as she desires to become an Olympic archer when she is old enough.
- ADHD: Like most demigods, she has superhuman reflexes.
- Dyslexia: Her brain is hard-wired for Ancient Greek instead of modern languages.
- Archery: As Apollo's daughter, she is a naturally talented archer, her skills only rivaled by her aunt, Artemis' maiden hunters. Kayla seems to take pride in her archery skills the most.
- Since Apollo is god of music, Kayla is a natural musician.
- She can curse others to only speak in rhyming couplets that can take days or even weeks to wear off.
- Biokinesis: As daughter of Apollo, she can heal people by singing to her father in Ancient Greek.
- She is skilled in physical contests and games.
- Kayla means Laurel in Arabic, suggestive of a reference to her father since the Laurel happens to be his symbol.
- In Greek, the meaning of her name is pure.
- Knowles is a common surname of Cornish origin that is said to be derived from the Irish surname “Ó Tnúthghail”.
- Kayla is the only daughter of Apollo known in the series.
- Kayla is the only known demigod with a human parent being the same sex as their godly parent.
- The way that she was born is unknown, not being known if Apollo is who was pregnant or Darren.
- She wishes to tryout for the Olympics as an archer.
- Kayla is technically the first Canadian demigod in the series to be introduced. Making Frank Zhang the second Canadian demigod to appear in the series. However, Kayla was only mentioned, in The Last Olympian, making Frank the first Canadian demigod to "appear" in the series.