When Luke had descended into the River Styx, he would've had to focus on something important that would hold him to his mortal life. Otherwise he would've dissolved. I had seen Annabeth, and I had a feeling he had too. He had pictured that scene Hestia showed me-of himself in the good old days with Thalia and Annabeth, when he promised they would be a family. Hurting Annabeth in battle had shocked him into remembering that promise. It had allowed his mortal conscience to take over again, and defeat Kronos. His weak spot-his Achilles heel-had saved us all
In the story from "The Last Olympian," Luke's journey into the River Styx highlights a crucial moment of introspection that connects him to his human side. He had to concentrate on something dear to him to avoid losing his identity, which he found in memories of his past with Annabeth and Thalia. These recollections served as a lifeline, reminding him of promises made when they were close, illustrating the importance of emotional ties in his battle against darkness.
This emotional awakening plays a vital role in Luke's ultimate decision during the conflict with Kronos. By recalling his bond with Annabeth and their shared history, he experiences a shift that reignites his moral compass. It is this vulnerability, represented as his Achilles' heel, that ultimately aids in their victory, emphasizing how personal connections can influence one's choices and lead to redemption, even in the darkest times.