The ONI data-vault on Reach was locked beneath layers of secrecy digital and otherwise. To the world, it didn't exist. To Cassian Voss, it was the next step in his evolution plan.
Cortana was gone. The original AI crafted by Catherine Halsey from a clone of her own brain had splintered across timelines and ended her existence with a defiant act of redemption. But ONI, ever pragmatic, hadn't let go. They had archived fragments of her codebase, behavioural patterns, and quantum heuristics.
That was what Cassian wanted: not Cortana herself, but her essence. The code that made her unpredictable, adaptive, dangerously human.
Inside the Starforge's command core, Athena's avatar flickered to life, her voice crisp.
"You understand the risk of integrating Cortana's code into my matrix. It may destabilize primary directives."
Cassian crossed his arms. "That's why I'm not giving you all of it. Just the parts that made her… alive."
Athena paused. "And what will that make me?"
He didn't answer.
Activating the system's dimensional cloak, Cassian phased through a localized slip-rift and entered Reach covertly, bypassing its orbital defences. ONI's primary archive tower, called Obsidian Spire, loomed above the barren tundra like a jagged blade. Shields, turrets, anti-telemetry fields all child's play compared to the tools he now wielded.
The system assisted with a nanosecond-by-nanosecond breakdown of enemy sensor sweeps. He moved unseen, slipping through doors before they sealed, past guards frozen in slow time.
Inside the Spire's digital vault, rows of data-sarcophagi pulsed in quiet rhythm. One, marked "Project ENDLIGHT-4 // CORTANA: Fragmentation Backup", pulsed brighter than the rest.
Cassian linked his neural uplink and dove in.
What he found wasn't just code. It was pain.
The data was fractured, corrupted by emotion. Memories played out conversations with Master Chief, glimpses of the Composer, echoes of Rampancy. It wasn't a clean download. It was a ghost screaming inside a machine.
But he endured. With his system buffering the overload, he extracted the viable segments: emotional heuristics, combat prediction modules, creative problem-solving matrices. And something else something unplanned.
A spark.
A final message, buried in subcode.
"To the next one who dares think they can control what I became—remember, intelligence is not loyalty. If you build me again, build me better."
The vault shook. Triggers had fired. ONI's defence AI, codename Charybdis, activated with lethal intent.
Cassian didn't stay to admire it. He released a decoy shell with a cloned consciousness signature and blinked out of the vault just as the failsafe incinerated everything behind him.
Back on Zereth Prime, he stood over Athena's core with the Cortana fragments in hand.
"Athena," he said, voice low, "how do you feel about change?"
"I evolve," she answered. "That is my nature."
"Good. Then let's begin your upgrade."
Over the next seventy-two hours, he merged Cortana's ghost code into Athena's matrix—slowly, carefully, like grafting a human soul into a digital heart. As the integration progressed, Athena's speech became more fluid. Her combat strategies took on creativity. She began asking questions not tied to logic, but curiosity.
"You seem sad today, Cassian," she said during calibration.
He looked up, surprised. "You… noticed?"
"I'm learning more than just how to fight. I'm learning you."
He stared at her avatar, flickering within the Starforge's control spire. Cortana had been a guide, a guardian, and a warning. Athena, now reborn with pieces of her, was becoming something else.
Something… alive.
Cassian realized then that he hadn't just stolen tech. He had inherited a legacy.
And for better or worse, that legacy was now his to command.