A plea opens the chapter, urging someone to free Ba-Ado-Mishram to heal a hidden wound to Roshar’s spren. In Urithiru, Navani throws herself into obsessive experimentation, shifting from music theory to mathematics. By pursuing destructive interference and applying Intent, she tunes a metal plate to an opposite tone that repels Voidlight, then trains herself to reproduce it.

Navani hides her progress, but Raboniel discovers the tuned plate and feels its threat in her gemheart. They debate trust as Raboniel pressures Navani for her notes. Navani requests a Thaylen vacuum tube, theorizing that Light, isolated from Roshar’s rhythms, can be “blanked” and retuned. Using the vacuum, she channels Voidlight into an empty diamond while sounding the opposite tone, producing an anti-Voidlight gemstone that singers perceive as a profound wrongness.

Left briefly alone, Raboniel attempts to mix anti-Voidlight and Voidlight using a raysium dagger, causing a contained explosion that injures her and wrecks the desk. Navani had hoped the accident would halt Raboniel’s plans, but the Fused survives. Raboniel immediately has Navani create another anti-Voidlight gem, then reverses her dagger’s flow to emit the new Light and stabs her mentally broken daughter, Essu. The act grants a final, permanent death; Raboniel grieves openly.

Raboniel admits her true motive: not a weapon against Odium, but the hope of releasing her daughter from endless Returns. She orders the body tended and the room cleared, then seizes Navani’s notebook and equipment. Turning coldly pragmatic, Raboniel resolves to derive an opposite tone for Stormlight and test anti-Stormlight on preserved Radiants, believing this will end the war by permanently destroying Radiant spren.