The excavation beneath the north tower ended at a door unlike any Rorak or Cally had seen: five concentric rings, each marked with a handprint, and beyond it the unmistakable sound of breathing. Rorak pressed his palm to the stone first, and the outer ring flared to life. Cally followed, her own touch kindling the second. Then came the glass sliver they had carried up from the ruins below, which woke the third ring when set against the door, and Cally's murmured prayer, which lit the fourth. It was only when they pressed their hands together against the final ring that the fifth caught, and the door swung open before them.
Inside was an obsidian hall unlike anything in the Glass City above. A black sphere hung suspended at its center, utterly still, and around it stood five glass figures, frozen mid-motion as though caught in the instant of the city's ruin. Cally recognized the shape of the working at once: a heart-binding, five living anchors bound into a seal meant to hold something. Something that could not be killed. Only contained.
When Rorak returned the glass sliver to the sphere, it slid into place like a key finding its lock, a missing piece of the binding that had somehow remained in the chamber all this time. The seal, which had been failing by slow degrees for centuries, steadied, at least for now. Then the handless figure spoke, its voice dry as old glass, and told them what the ruins themselves had refused to say: a mage named Iskandra had vitrified the entire city in a single desperate instant to trap an entity that lived between moments, a thing older than the walls it haunted. She had believed she could destroy it. She had been wrong. She fled north afterward, carrying six binding shards with her.
Her sanctum, the figure said, stood at Still Peak in the northern mountains. Five shards remained there, or wherever her flight north had scattered them, and the seal she left behind would hold for months, perhaps a year, before it failed. Rorak felt something stir in his own chest at the words, an old, familiar pull, the same resonance he'd felt before without understanding why. Whatever bound him was not the same magic as this heart-binding, but both were prisons, and he could not shake the feeling that Iskandra's knowledge might hold answers he'd been searching for far longer than this journey.
They left Torunn, Mathis, and Fenna to stand watch over the tower entrance and climbed back up into the daylight, weighed down by more questions than they'd descended with. In Dusthollow they resupplied and spoke with Zahira about the roads north, and felt the changes settling into them, both of them stronger now, seasoned by what they'd survived beneath the glass. As dusk fell over the encampment, they turned their faces north into the Scorch, toward the Needle trail, toward Sandgate, and toward whatever answers Still Peak was keeping.