They made it forty kilometers from the Archives before stopping. Found a hollowed hill with a concealed entrance that Omen identified from memory as an old Architect waystation, similar to the one outside Ashenveil but deeper underground, better shielded.
Kael set down the complete Core and sat with his back against the wall and breathed carefully around his ribs until the worst of it faded.
"Tell me," he said.
Omen knew what he meant. He'd been waiting.
"The resonance cascade," Omen said. "When the complete Core detonates within sufficient proximity to the World-Ender Gate — about ten meters — it generates a frequency that dismantles the Gate's foundational architecture. Every component, every activation circuit, every five centuries of enhancement. Gone." He paused. "The cascade propagates outward through every dark-energy channel Malgrath has built — the towers, the embedded agents, the void-anchors. Everything Malgrath has spent five centuries constructing is dismantled in approximately four seconds."
"And the host," Kael said.
"The cascade requires a living, bonded host to serve as the initiation point. The host's life force is the primer. Without it, the cascade cannot achieve sufficient resonance." Omen's voice was very careful. "The host does not survive the detonation."
Silence.
Lyra, across the room, had gone very still.
"You knew," Kael said to Omen. "When you told me to pick up the compass. When you said the Engine would choose its bearer. You knew the bearer was choosing to be—"
"I knew the possibility," Omen said. "I did not know the certainty. There are configurations, at the extreme end of what the Core can do, where survival might be possible. I have spent five centuries running the probability calculations. They are not encouraging." A pause. "I did not tell you because a person who knows they are walking toward their death changes how they walk. I needed you to be fully present, fully committed, fully alive right up until the moment when the alternative becomes necessary." He paused. "I am sorry. That was a choice I made, and you deserved better information."
The silence extended.
"Also," Omen said, and his voice was quieter now, more careful, "I know what it is to have built something that destroys the person who uses it. I have lived with that knowledge for five hundred years. I did not want to give it to you any sooner than necessary."
Kael looked at the complete Core. At the three components now fully integrated — the Engine he'd bonded with, the Sigil that Lyra carried, the Voice they'd recovered. Something built by Omen. Something built to fix Omen's greatest mistake. Something that required everything its bearer had.
"My parents," Kael said.
"Malgrath took them because your bloodline was flagged as a potential Engine-bearer. That is true. But it also means they are almost certainly being kept alive — useful as leverage, useful as motivation." Omen paused. "If Malgrath is destroyed, his holding facilities lose their maintenance. Whatever prison they are in would automatically release its occupants."
Kael nodded slowly. Filed it.
Lyra stood up. Walked to him. She crouched in front of him, elbows on her knees, and looked at him with the kind of direct, honest gaze that she used when she'd decided that something important needed to be said and politeness wasn't going to help.
"We're going to find another way," she said.
"Lyra—"
"I'm not accepting a conclusion where you die in the last chapter. That's not what's happening." She held his gaze. "We have three pieces of the most advanced device ever built by a civilization that could do things we can't currently explain. Omen designed it five hundred years ago and he's been running probability calculations with the same information ever since. We have information he doesn't — current knowledge, current capability, the actual system assembled for the first time." She paused. "We are going to find another way."
He looked at her for a long moment.
"You sound very sure," he said.
"One of us has to be," she said. "You can be sure about the plan. I'll be sure about you surviving it." She stood up. "Now rest. We need to cover forty more kilometers tomorrow and your ribs sound like gravel when you breathe."
Kael leaned his head back against the wall.
"Omen," he said.
"Yes."
"Run the calculations again. This time with Lyra as an input variable."
A long pause. "She cannot—"
"Run them."
The compass was quiet for a while. The kind of quiet that might have been computing.
Then: "There is one configuration," Omen said. Slowly. "Highly theoretical. It has a seventeen percent probability of being feasible and I have never attempted to validate it because it requires a simultaneous alignment of all three components and a shared resonance field between two users." He paused. "It is very unlikely to work."
"Seventeen percent," Lyra said from across the room, without looking up from where she was laying out her sleeping roll. "Better than zero."
"Significantly better than zero," Kael agreed.
From the compass, something that might have been relief — quiet, ancient, carefully suppressed.
"I'll run the full calculation," Omen said. "Give me until morning."