Simple. The first Halo ARG was extremely limited, but it took place before the first game was even announced. It began Febuary 16th, 1999, with an email from a prominant Marathon community member. Marathon was a trilogy of story-heavy FPS games for the Macintosh staring a nameless security officer fighting hordes of aliens while working with the snarky, greedy, scared, homicidal and awesome AI Durandal, and was made by Bungie Studios, the makers of Halo. Durandal was a "rampant" AI, which in the Marathon and Halo universes is an AI that has entered a form of insanity, marked via three stages and a hypothetical fourth. These are (with various names, but all the same meaning) Sadness, Anger and Envy.
In the first, the AI becomes depressed, realizing its limitations and realizing it will never be truly alive. In the anger stage, the AI instead lashes out. This is the stage in which most rampant AI are discovered. In the envy stage, the AI harbors a deep jealousy for humanity, because of their nature. However, there is one final stage, meta-stability, in which the AI essencially calms down, and becomes much more powerful, and far more intelligent, beyond human comprehention. It's typically called the "Holy Grail of AIs". Durandal was intentionally made rampant, in an attempt to create a meta-stable AI. Able to run a planet, he was put in charge of the doors on the UESC Marathon, a simple and extremely limited task. This did not end well.
Now, for Halo fans, this is becoming a tad more familiar. Cortana is rampant in Halo 4, and this is made quite clear. In fact, she goes through the phases throughout the game, ending it either meta-stable or in the envy phase. Now, one may think that there is no possible way that they planned this. But, they did. They have said numerous times that they have a "Halo Story Bible" that contains pretty much the entire plot and expanded universe information. One example of this is the offical site certa the release of Halo: Combat Evolved. The official timeline talks about humanity discovering planets with humans on them that the UNSC, the Halo universe government, knew nobody had ever been to. Weird tidbit that sounds like a creepypasta? No. Decade-in-advance foreshadowing? Yes.
About a decade later, the Forerunner Trilogy of novels revealed that, a hundred thousand years ago, humanity had a vast empire, made up of a partnership between humanity and the San Shyyum, also known as the Prophets, the future leaders of the Covenant. This empire discovered the Flood. The Human-Flood War began, and as they lost planets to the Flood, they invaded and stole Forerunner planets. In response, the Human-Forerunner War began. Humanity beat the Flood, but lost to the Forerunners. The Forerunners stranded humanity and the San Shyyum on their respective homeworlds, and kept them at a low technological level. However, in the face of this, humanity still refused the Forerunners the one thing they desired: the Flood cure. With humans still on some planets, kept there by the Forerunners (in fact, one settlement was even on a Halo), it's likely that their communities were reseeded via the activation of the Halo Array, which is why they were there.
Now, what does this have to do with Cortana? Well, in 1999, as said before, one of the leading members of the Marathon community got a curious email from firstname.lastname@example.org, the first of several. However, this was not the only Cortana email address. Weirdly Cortana sometimes used email@example.com, which another Bungie email was disguising itself as and sending Cortana letters through. JPL is the Jet Propultion Labrotories. The Cortana in the Cortana Letters however, is not the well-composed Cortana fans know. While personality traits remain, it's twisted. This Cortana is rampant. This Cortana takes much more glee in wrecking the (then unnamed) Covenant. This Cortana considers herself a goddess, and jokes about coverting the Covenant's gods, the long dead Forerunners to worship her, in an email from another NASA email, relay.arecibo.nasa.gov.
Now, obviously, you're thinking that NASA was pranking people. However, these emails contain references to the Halo franchise's story and backstory, stuff that would not be revealed for years. The game was stull untitled and going by the codename of "Blam" (side note: nobody knows who came up with the title Halo, as it appeared on the whiteboard for title suggestions and nobody took credit for it). Additionally, unlike last time, this email did not exist. The technical lead for AOL's email at the time broke it down and explained it on the site. The time stamp was also from several years in the past. Addtionally, this Cortana seems to not have a handle on the order of events or even when/where she is. "I am now sharing cramped space with the circuitry of some hybrid war machine, itself complicated by such useless clutter as a conscience" she says, obviously refering to her first placement within John, but with a more callous mindset.
But, there's one more aspect of this Cortana that one must take into note: her love of poetry. In the Halo universe, she never really expresses much interest in poetry. In the Cortana letters, there are numerous poetry references. Now, someone yearning to be human instead of just a machine would be drawn to our creative side, because she could learn from it. However, there's one other character in the Halo universe who is a poet. One character who will only speak in rhyme. The Gravemind. The Flood hivemind. He had her captive for quite a while, and likely instigated her rampancy. Their time together is detailed in a short story in a compilation book of Halo short stories. It is a horror tale, one the games aren't dark enough to get in to.
A hidden Cortana message also talks about the lost human colonies. And, just to get further into it, in the Halo: Legends anime, two parts are Cortana telling the histroy of the Forerunners, humanity and more. But, as she's going rampant, she gets details wrong, even ones she was there for. In her story, Gravemind gives her back to John. Legends was released years after Halo 3. Either Cortana can't remember, which is impossible, or has repressed the memories of her time with Gravemind, which is also impossible, or the rampancy has damaged her quite a lot, causing similar cronological errors and personality shifts like those in the Cortana Letters and in Halo 4.
So, what on Earth is this leading up to? Well, for quite a while, the Cortana Letters have been confusing and out of character. However, in Halo 4, Cortana "dies". She combines with Forerunner technology, much like Durandal's "death" in Marathon: Infinity, in fact, in which he merges with another AI and loses the name Durandal, although keeping his personality. However, Cortana is implied to be destroyed.
The thing is, the Halo 5 trailer shows that John is looking for her, on his own. He's on a personal mission, his helmet is damaged, he seems to be on a foreign planet, and he's even got a cloth cloak on over his armor. But, John will not find the Cortana that he has come to know, the Cortana that's saved his ass and whose ass he's saved. John will not find the Cortana he invaded the Flood-controlled High Charity either alone or with the Arbiter (canon's vague on whether or not the Arbiter being there in co-op is canon, but it certainly contributes to their own stories) to save. He's going to find a broken shell of a Cortana, with godlike powers and no idea where or when she is, a Cortana who apparently has the ability to trasmit data through time, and considering the Cortana Letters exist in our reality, and she does make occasional references to changing the future, perhaps dimentions.
I've been trying to figure out how the Cortana Letters fit into the Halo universe for seven years. It feels like I've completed my own personal quest. Also, how very fitting, with Bungie's 7 fetish. I know they no longer control the franchise, but the series still uses things like the Marathon logo. So, yeah, that was extremely long, I feel, but I needed to explain everything, since it's a theory going not only in to the expanded universe, but the fringe parts of it. I need some sleep. PosthumanHeresy (talk) 04:22, February 26, 2014 (UTC)