Ember and Ky navigate the upper halls of the mountain, surviving shadow-birds and magical barriers, until they reach the Hall of Justice and the Book of Echoes. The book demands spoken truth and reacts violently to the presence of Ky, physically slicing her face with invisible claws while echoing a rhyming curse that accuses her of devouring human flesh. The emotional gut-punch lands when Ember, influenced by the twisting magic of the book and his own buried fears, grabs Ky by the shoulders and demands she confess to eating his people. Her silence confirms his worst suspicions. He abandons her bleeding in the dark, taking his glowing stone and leaving her to the whispers of the mountain. This betrayal breaks the fragile romance of the narrative and flips the dynamic entirely. The corrupted magic of the book preys on the insecurities of Ky, twisting her mind into a feral, predatory state where she decides she must hunt Ember down. She tears pages from the book to silence its mocking echoes, but the damage to her psyche is already done. The book operates on a strict magical rule that forces absolute honesty, weaponizing the hidden guilt of Ky against her. When she tries to physically destroy the book by ripping out its pages, the sentient artifact uses her own stolen voice to mock her, driving her into a predatory frenzy. The unresolved tension here is lethal. Ember is now alone in a maze of illusions, armed only with a wooden spear and his own terror, while the very creature he trusted is stalking him through the dark with murderous intent. He must navigate a hall of shattered mirrors where his own dripping blood gives away his position to the feral siren, turning a story of unlikely companionship into a desperate game of survival.

Fleeing a mind-bespelled Ky through a hall of mirrors, Ember locks himself inside the Oracle Sanctuary. He heals his torn back with magical crystals and, desperate for answers, breaks a dead oracle bone to force the scrying well to show him the location of Ky. Instead of her present, the well projects a past vision of Ky and her older sister, Sil. Ember watches in horror as Sil tricks a starving Ky into eating a stew made from a human man named Bren, a brutal hazing ritual meant to force the becoming of Ky into the cannibalistic hierarchy of the clan. The magic of the well is so potent that it bridges time, allowing the past iteration of Sil to lock eyes with Ember in the present and threaten to flay him. This milestone completely recontextualizes the character of Ky. She is not a remorseless monster, but a traumatized runaway who fled her clan to avoid eating humans and suffering the wrath of her sadistic sister. The social hierarchy of the sirens is revealed to be built on dominance and the consumption of human souls, making Ky an outcast among her own kind. Armed with this profound empathy, Ember leaves the sanctuary to track the bloody footprints of Ky. He shifts his goal from mere survival to actively protecting the siren who brought him here, stepping back into the dark to face the very monster he was running from. He finds her huddled in a forgotten room, starving and terrified of her own nature, and offers her his last healing crystal. This act of grace rebuilds their shattered trust and cements their bond, proving that Ember sees her as a person rather than a beast.

Reunited, the pair enters a massive cavern of hoarded gold where an ancient, mutated siren ambushes them. The creature, driven mad by centuries of isolation in the dark, mistakes Ky for his dead lover Mohe'na and attempts to eat Ember to claim his song. The fight forces Ember to use the runeblade Fishbiter, a magical sword he scavenged that burns siren flesh upon contact. The ancient siren is a terrifying force of nature, using a booming, baritone hum that vibrates the very stones of the mountain and incapacitates Ember with sheer sonic force. When the monster corners him, Ky uses the glowing tree-stone to blind it, allowing Ember to drive the blade through its heart. The emotional climax occurs in the bloody aftermath, where Ember vomits from the trauma of his first kill, grappling with the heavy reality of taking a life. Ky finally confesses her true motive in the quiet that follows. She is not looking for gold, but a lost human treasure that her elder claimed would fill the spiritual void that forces sirens to eat human hearts. This revelation chains directly into their next move. They must push deeper into the lethal lower levels of the mountain to find this mythical cure before the starvation of Ky drives her mad, transforming their journey from a simple escape into a quest for the salvation of her entire species. The death of the ancient siren also strips away the last of the false guardians of the mountain, leaving them exposed to the harsher, more desolate environments of the deep tunnels, where the air grows hot and the shadows stretch longer.

The descent turns brutal when they enter a wind-tunnel filled with the desiccated bones of sirens trapped by ancient human heat-spells. The environment is a functional manifestation of the ancient war between humans and sirens, using baked stone and relentless, drying winds to dehydrate the river-folk. Ky begins to wither from the extreme conditions, her skin cracking and flaking as her biological need for water overwhelms her magic. In a desperate act of sacrifice, Ember carries her through the storm, repeatedly spitting his own moisture into her mouth to keep her alive until they reach the subterranean salt baths. While Ember sleeps to recover from his exhaustion, a recovered Ky follows a magical resonance into a hidden vault, discovering glass jars containing trapped, glowing human souls. A massive shadow entity manifests from the sulfurous mist, revealing that the sirens did not just eat humans, but originally shattered their mortal cages to harvest their souls for a dark pact. The entity mocks the ignorance of Ky and claims the souls as its own sustenance. This cliffhanger shatters the understanding Ky has of her own history and presents a terrible choice. She must either claim a soul to cure her hunger and embrace the monstrous legacy of her ancestors, or free them and remain a starving outcast forever. The entity recognizes her as a rivensoul, a term that hints at a deeper, darker origin for the siren race that the elders deliberately hid from the younger generation. Ky stands paralyzed by the whispering chorus of the trapped souls, her predatory instincts warring with her newfound morality as the shadow prepares to defend its hoard.