Raboniel grants Navani space to work, slowing Fused progress on the Sibling’s shield without Navani as an unwitting spy. Isolated from administration and her scholars, Navani decides to embrace pure research, aiming beyond saving the tower to potentially ending the war by discovering anti-Voidlight. She orders supplies, practices humming Warlight with Raboniel, and constructs hidden fabrial traps disguised as experiments, armed by magnets and fueled with Voidlight.

Seeking opposites she can measure, Navani requests stronger magnets and a metal used to draw out Stormlight. While waiting, she experiments on a conjoined ruby—its spren split across halves—trying to rejoin it using tones. A stormform guard fetches her requests as Raboniel’s daughter watches, humming a human tune, while Navani observes the corrupted flamespren respond to a tuning fork but remain trapped behind the gemstone lattice.

Raboniel arrives with a raysium dagger, explaining the metal conducts Investiture, can drain Radiants, and—after Ba-Ado-Mishram’s fall—was purposed to trap Herald souls; one Herald has been taken, though with complications. The dagger contains only a small amount of raysium. Navani tests it: breaking one half-gem frees the half-spren, which the dagger immediately captures. Moving the dagger then yanks the other gem half much farther, revealing that unequal gemstone sizes create force multiplication in conjoinment.

Navani and Raboniel formalize the observation—energy remains conserved but motion is amplified on the smaller mass—and agree to document the discovery, which Raboniel dubs part of the Rhythm of War. When Navani asks how to quantify Light, Raboniel promises black sand that turns white in Investiture’s presence. Praising Navani’s capability, Raboniel departs, leaving Navani committed to pushing her research toward a weapon—anti-Voidlight—that might end the conflict.