Believing Bjorn dead, the remaining travelers take refuge inside the Felrune Bridge's central tower while the undead rook circles outside. They find a recently slain pilgrim wearing the symbol of Pludex, evade the bird's beak and talons, and climb past a Dregda Moor revenant that Torrin shoves from the tower. At the summit, Whisper fires the tower's single ballista bolt. The ancient weapon explodes, but its shot tears through the rook's wing and sends the creature crashing into the tower and then into the chasm. Far below, the young Magda Navaa treats Bjorn's wounds and explains that she and her unseen sisters have guarded the mire for a very long time. She says the wind has revealed the consuming fire, rage, and pain within him, then leads him through an autumnal refuge to a wall of thorns. Bjorn must choose between embracing the rage, culture, and strength that have defined him or surrendering them for a harder path of temperance. He relinquishes his anger, sees Magda briefly assume the elderly form he remembers, and walks through the thorns to the exposed root of an impossibly vast tree dripping gold. Five pieces have been harvested from the root, including the wood used for Helvegen's haft. When Bjorn touches that scar, Kypheron's flame and his barbarian rage erupt from him, burning the root and blasting a pillar of fire through the plateau. The conflagration melts part of the glacier around Drag'Dah and leaves Bjorn without his former abilities, but with the beginnings of a new inner power.

The travelers cross the rest of the bridge and approach Drag'Dah's black, handleless doors. Torrin recognizes the keep as a late Veyan cathedral devoted to Sethis, built around the passage from light through darkness into twilight. His compass points directly into the fortress, and the Crystallic causes the black door to burn white and open. Meanwhile, Bjorn returns to the ruins of Magda's cottage, enters the bridge tower through a door buried beneath the mire, equips himself from its ancient stores, and climbs thousands of feet to the surface. He reunites with the companions inside Drag'Dah and explains his choice, the loss of Kypheron's fire, and Helvegen's origin. The weapon now emits unavoidable golden light whenever he holds it. In an immaculate dining room, that light attracts a savage, luminous apparition that drains warmth and life. The party destroys the creature with radiant power, and Rue identifies it as one of the Shadowless, beings made entirely of light because they have no shadow. Their counterparts, the Lightless, are beings made entirely of shadow. Rue remembers that Sethian devotees used a prism chamber in an attempt to become twilight beings, but instead tore their souls into separate halves. He fears Drag'Dah and initially recoils from the possibility of reuniting with his own missing half.

A concealed candelabra opens stairs into the crypts, where the travelers find ancient Veyan construction altered by the Dregda Moor. A Lightless shaped like Rue confirms that the other half of his divided existence is somewhere within the keep. Elsewhere, the party discovers skeletal Dregda Moor huddled beneath desperate wards and the repeated warning that they called something from the darkness. Further rooms contain an aquatic embryo frozen in the kitchen, an empty armory, and rows of blank canvases from which all Veyan art has vanished. Torrin unlocks a black door patterned with blue-lit flowers and enters a sealed room where a timid Veyan boy of light circles an urn. Rue recognizes the figure as his body, but the two halves cannot merge by touch alone. Opening the urn briefly restores the chamber for Torrin and reveals the boy's mother, trapped in perpetual twilight. She says she was misled, asks her lord to save her son, and pleads with Torrin to remember her before darkness with green eyes closes around the vision. Torrin places the Crystallic between Rue and the boy, joining their light and shadow. A partial band of light forms across Torrin's brow, Veyan art and architecture return within a twenty-foot circle, and Rue becomes a living child who shares a sustaining bond of memory with Torrin. The restoration unlocks Torrin's remembered nature, but leaves the mother imprisoned and the force that destroyed Drag'Dah unresolved.