I don’t think I should need to say this, but… THERE ARE A LOT OF SPOILERS ABOUT TO BE DROPPED if you haven’t read the books or played Halo 4. So. Be ye warned!
PART TWO: On Genesongs
First off, what the heck is a Geas/genesong? A genesong is a genetic compound imposed on an organism or species. The term itself, “Geas (ge-ah-sh)”, was a Forerunner term, describing the essence of life that the genesong encompassed.
A geas could range from monuments of wisdom and knowledge all the way up the literal mental copy of a particular being’s mind and soul. A geas could be immediately activated, once passed to its new “host”, or it could be locked away within the host or its descendants until certain mental or physical queues, either internal or external, triggered its awakening. Under the influence of a geas, an organism could be given a set of subconscious instructions, details, or orders that would be specific to that organism, or passed on to their offspring, sometimes for a single generation or even down through several generations or more. The procedure of imposing a geas on a life form was conducted (see also: composed) by the skilled hands of Lifeworkers, a Forerunner rate that was tasked with the keeping and preservation of all life throughout the Galaxy, as a most-direct means to uphold the Mantle.
At the closing of the Human-Forerunner war, the Didact ordered many of the strongest and finest human warriors be composed and kept alive as a library of geas testimonials, in the hopes that they could learn how to stop the advance of the Flood. It wasn’t until near the end of the Human-Forerunner war that the Didact realized that the humans weren’t on a march of imperialism- they were trying to eradicate the Flood by “glassing” whole planets where they found the infection. But upon their capture, these human warriors refused to give up their secrets to fighting to the Flood, so, they were composed and transformed into genesongs to be used as a geas in selected humans for later review and revelation.
One of these humans was named Chakas. Another named Riser. (You can read about their story in Halo: Cryptum), but tl;tr- Chakas had been imprinted with the geas of the Lord of Admirals, the most supreme arch enemy to the Didact himself, and harborer of the secrets to the Flood’s defeat, or so the Forerunners assumed. Riser was also imprinted, but his geas is where the fun truly beings…More on that later.
Along with a young rebellious Forerunner named Bornstellar, Chakas and Riser happen across the Cryptum of an old Warrior-Servant, who happens to be the Didact himself. Knowing that his judgment will arrive swiftly, the Didact imprints himself onto Bornstellar, and Bornstellar immediately begins to feel the effects. What the Didact basically does here is make a copy of himself, via his geas, that eventually transforms Bornstellar into Didact #2, aka, the IsoDidact.
**So now we have: **
Ur-Didact -> IsoDidact[/li]
Lord of Admirals -> Chakas[/li]
I won’t go into the novels too much because tl;tr here- seriously, go read them! They’re fantastic!- but what eventually happens is that Chakas ends up being composed and turned into a monitor, the same Forerunner monitor we know as 343 Guilty Spark. The IsoDidact gives a geas to Riser, but it isn’t clear whose it belongs to or whom it originally came from.
Riser was given a long-germination type geas of the IsoDidact himself, a geas that wasn’t meant for Riser directly, but for a human descendant a few generations later, the same human descendant we know as Spartan John-117.
Woah, wait, what??
In Halo: Combat Evolved, 343GS says to Master Chief, “Last time, you asked me, if it were my choice, would I do it? Having had considerable time to ponder your query, my answer has not changed.”[/li]
In Halo: Primordium, IsoDidact says to 343GS, “Tell me, Chakas, if this was your choice, after all we have seen and survived… would you fire the rings?”[/li]
It’s been long speculated that 343GS was going rampant, given his seemingly random and unmoored comments during the time you are escorted by him through HCE. I challenge that, and offer the possibility that 343GS was seeing something within Master Chief, via 343GS’s geas of Chakas, and through the still 99% dormant geas of IsoDidact-aka-Bornstellar within John-117.
So- as Master Chief continues to evolve and become the Reclaimer he was destined to become through his geas, we might indirectly see the return of IsoDidact-aka-Bornstellar, but not in the most physically obvious way.
**So now we have: **
Ur-Didact -> IsoDidact -> Riser -> John 117[/li]
Lord of Admirals -> Chakas -> 343 Guilty Spark[/li]
And! Bonus round:
Librarian -> Chant-to-Green -> Vinnevra -> Catherine Halsey -> Cortana[/li]