Luke Castellan is the demigod son of Hermes and Athena. He is the brother of Annabeth Chase.
Luke was the head counselor for Cabin 11 before the Olympian War.
Not too long before the cataclysm that rocked the world during Hermes was allowed to bring his son back from the Underworld.
Following his return, he was tasked by his father and Olympus to return to Earth to aid the demigods that had gathered at Crystal Dawn.