Set roughly two months after the events of The Tower of Nero, The Sun and the Star follows two demigod boyfriends: Nico di Angelo, son of Hades, and Will Solace, son of Apollo. Nico is haunted by a voice calling to him from Tartarus, the deepest and darkest pit of the Underworld. He becomes convinced it belongs to Bob, a reformed Titan named Iapetus whom Percy Jackson and Annabeth Chase were forced to leave behind during their own descent into Tartarus years earlier. When Oracle Rachel Elizabeth Dare delivers a new prophecy, one warning that the journey will require leaving something of equal value behind, Nico resolves to descend and rescue his old friend. Will, a child of sunlight and healing, insists on going with him, even though a being made of light has little business surviving in the world's darkest place. The novel is a standalone adventure that doubles as an intimate character study. As the couple travels deeper into Tartarus, the hostile landscape strips them down to their rawest selves, surfacing buried fears, past trauma, and tensions in their still-young relationship. Riordan co-wrote it with Mark Oshiro specifically to render Nico's perspective as a gay teen, and the central romance, with authenticity. It deals candidly with mental health, portraying Nico's depression and PTSD and framing the descent as a metaphor for struggling with intrusive thoughts, while showing healing as a messy, ongoing process supported by friends and chosen family.
