Deeplight

Deeplight is set in a world where gods once existed beneath the sea but destroyed one another fifty years before the novel begins. Fifteen-year-old Hark discovers the still-beating heart of one of these dead deities and attempts to use its power to save the life of his best friend, Jelt. The narrative follows Hark as he tries to keep the artifact away from smugglers, scientists, and cults, while confronting the consequences of what the heart's power does to Jelt.

The novel centers on a layered cosmology in which an undersea realm was the dwelling place of divine beings known collectively as the Myriad. Remnants of these gods — even small fragments — are described as carrying strange powers and commanding significant value. The setting draws on a maritime environment where the boundary between the upper sea and the undersea carries mythological weight, and where the gods' unexplained mutual destruction shapes the culture and economy of the world Hark inhabits.

Central themes include loyalty, the limits of friendship, and the dangers of wielding power beyond human capacity. Hark's relationship with Jelt is the emotional core of the plot, as Jelt undergoes a disturbing transformation after exposure to the god's heart. The story raises questions about what one person owes another and what sacrifices are too great to make. The presence of competing factions — smugglers, scientists, and religious cults — adds a dimension concerned with how power over the divine is sought and contested.

Deeplight is a standalone novel published under the author name Frances Hardinge. The publisher description positions it as a young adult fantasy, with a fifteen-year-old protagonist at the center of the narrative. The book involves themes of mortality, transformation, and moral choice presented within a secondary-world fantasy framework built around oceanic mythology and the aftermath of a divine apocalypse.