While she doesn't play a major role in the book itself, she is a significant character in the larger *Percy Jackson & the Olympians* series.
Here's why:
* Her Importance: Thalia is the daughter of Zeus and a Hunter of Artemis. She was Percy's friend at Camp Half-Blood and was turned into a pine tree by a monster to save Percy and Annabeth.
* Her Connection to the Plot: Her presence in the story is key to understanding Percy's journey and the prophecy surrounding him. The prophecy, which involves a child of the Big Three (Zeus, Poseidon, Hades), being the only one to stop the war, hints at Thalia's significance.
* Her Role in Later Books: Thalia's story is further explored in later books in the series, and she plays a crucial role in protecting Camp Half-Blood.
While she may not appear directly in *The Lightning Thief*, her influence and connection to the story are undeniable.