At its E3 showcase, Microsoft showed fresh footage from Halo Infinite's campaign, raising intriguing questions about the fate of Master Chief's companion, Cortana. The ending of Halo 5: Guardians sets up the once-benevolent, then rampant and rogue AI as the greatest threat facing the Halo universe before Halo Infinite. Disillusioned with humanity due to their warlike tendencies—and possibly compromised by Forerunner technology—Cortana was poised to conquer the galaxy with the aid of Forerunner Guardians, Halo rings, and other AIs defecting from the UNSC in a bid to achieve galactic peace through overwhelming force.

The narrative trailer begins with John-117, AKA Master Chief, navigating the debris of a ruined ship. As he jumps from makeshift platform to platform, Cortana's voice haunts him with questions, such as "If you knew you how you were going to die, how would you live your life differently?" Eventually, Chief arrives at a command room, encountering a new AI who also loosely resembles a young Dr. Halsey and might therefore be considered a descendent of Cortana. Their conversation is where things get interesting.

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Chief demands to know where Cortana is, and the new AI replies, "The rogue AI known as Cortana is gone. She's been deleted." Chief asks if the new AI is responsible, which confuses her, as Chief seems to have forgotten their respective orders. She explains that she was supposed to infiltrate Cortana's installation through imitation, disable her, and prep her for retrieval, while Chief was supposed to take Cortana back to the UNSC Infinity for deletion. Furthermore, the new AI had an auto-deletion protocol that was supposed to activate, which has been forestalled for some reason. Chief states that the mission has changed, offers the new AI his data chip, and slides her into his head.

Rampant, Rogue, or Something Else?

Cortana, and all other UNSC AI constructs, are destined to have a seven-year lifespan before they are consumed by erratic, dangerous behavior known as rampancy. The condition is a sort of mental degradation paired with megalomania, where the AI gradually grows to despise its human creators. Throughout Halo 4, she wrestles with this condition, which exhibits itself in variety of ways, ranging from delusions to schizophrenia, until her self-sacrifice to rescue Master Chief.

In Halo 5, it is revealed that Cortana was uploaded to the Domain—essentially a Precursor internet leveraged by the Forerunners—where she is supposedly cured of her rampancy, and now functionally immortal. Furthermore, Cortana accepts the Mantle of Responsibility: the Forerunner creed that asserts that the single most advanced species or entity in the galaxy assumed responsibility for—and dominion over—all other life in the galaxy.

While Master Chief is initially glad to see that Cortana had survived her apparent deletion, Dr. Halsey deems her unreliable, and her suspicions prove to be well-warranted. After being uploaded to the Domain and accepting the mantle, Cortana began to court other AIs to her cause with the allure of immortality. Together, this cabal of AIs began activating the Guardians, massive Forerunner constructs designed to "police" worlds during the Forerunner's Ecumene, resulting in the destruction of several human colonies, and the loss of countless lives.

Fighting Digital Gods

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Things looked bleak as the curtain closed on Halo 5: Guardians' Legendary Difficulty ending, with Cortana blithely humming as a Halo installation warmed up. But supposedly, three in-universe years will have passed when Infinite kicks off, so it is difficult to know what became of her conquest. Master Chief, Thomas Lasky, and the other good guys only managed to escape her wrath with a sequence of randomized slip scape jumps, making it one of the last bastions of rebellion against Cortana.

But how is humanity supposed to fight a coalition of entities with no physical form, unrestricted access to data networks across the galaxy, and overwhelming conventional firepower at their disposal? One surprising answer may be The Covenant, under new management courtesy of the Arbiter's Sword of Sanghelios. With the prophets and Jul 'Mdama killed, the Arbiter may be the new de facto leader of the Covenant, at least as far as military operations are concerned. Covenant forces have proven themselves to be a match for the full might of the UNSC earlier in the series, and have become an invaluable ally to humanity since. Their forces could plausibly buy humanity time.

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Another potential strategy is teased right in the trailer: suicide bomber AIs. With Cortana turning longer-lived AIs to her side, it is highly unlikely the UNSC could rely upon their sentient, self-aware super-intelligences unless they were designed with timed or conditional self-deletion commands that would take them out of commission before they are turned by Cortana or "cured" by the Domain. But who is this new AI? And how did she survive her kill switch?

Cortana: The Possibility of Redemption

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Given that Halo Infinite has been described as a "spiritual reboot" of the storied franchise, it is entirely possible that this AI is the series "new Cortana." Just like the original, it stands to reason that she would be capable of feats that other AIs can't hope to pull off, which might explain how she subconsciously halted her auto-deletion protocol. That possibility becomes even more likely if Master Chief hangs up his helmet at the conclusion of the end of the game. And there is a strong argument that Infinite should be Master Chief's last game, as his age means it's nearing time to put up the helmet.

But is there any hope of a happy ending for the series' original pairing? Cortana has definitely pulled a mean heel turn, but her dying a villain's death would likely leave a sour taste in the mouths of Halo fans. Bearing that in mind, it isn't hard to imagine a scenario where Cortana divides against herself at the eleventh hour, either as a virtue of her unique capacity for metastability, or a lingering effect of her maybe-not-cured-after-all rampancy. Halo fans will have a hard, but relatively brief wait before they can find out.

Halo Infinite is scheduled to launch for PC, Xbox One, and Xbox Series X/S this holiday season.

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