Confined in Urithiru, Navani receives stacks of texts at Raboniel’s order and continues sending mundane instructions to her scholars, hiding ciphered nonsense to misdirect Fused scrutiny. Immersed in optics, she replicates prism experiments: candlelight splits into a rainbow and can be recombined; Stormlight yields a spectrum with an enlarged blue band; Voidlight produces a spectrum dominated by violet. Towerlight—gathered from the Tower—splits into two distinct spectra. Navani cannot recombine them, resulting instead in overlapping white-blue and white-green beams she suspects correspond to Stormlight and Lifelight.

Prompted by these results, Navani revisits journals from the day of Gavilar’s death, recalling strange, “negative” glowing spheres and his scornful claim that she was an opposite that “destroys light.” She wonders if Gavilar possessed Lifelight and had knowledge of other, alien Lights.

Raboniel arrives with an often-present, unstable Fused. Navani demonstrates her findings; Raboniel confirms the Towerlight theory and presses a central question: can Stormlight and Voidlight be mixed? Claiming a desire to end the interminable war, Raboniel outlines a hypothesis of opposites—negative axi and a potential anti-Light—asserting that a Light and its anti-Light would annihilate on contact. Navani, recalling a volatile sphere entrusted to her scholars, worries prior tests may have triggered a destructive reaction.

Raboniel promises to free the tower if Navani learns to combine the Lights, while Navani doubts the offer yet recognizes the strategic value of the knowledge. As Navani gropes for a metaphorical “emulsifier for light,” the unstable Fused speaks to the wall, asking for her mother. Raboniel quietly reveals the truth: the unhinged Fused is her daughter, a personal tragedy that complicates the Lady of Wishes’ relentless pursuit of dangerous discovery.