This may be a long post.
I personally like The Ark theory that has been around since the teaser trailer.
John’s on the Ark looking for Mendicant Bias to help stop a Flood Invasion.Which is why “All our lives are at stake”. Further more, the Ark is also the likely home of the Absolute Record. MB and the AR could be one in the same, but I think they are separate entities.
We know the UNSC ship Rubicon returned to the ark and found 343 “Chakas” Spark According to the 4th “11th Hour Report.” further more, that report details the current condition of the Ark.
This passage in particular makes me think of what we see in the teaser trailer:
The damage was… traumatic. Habitability sustainment systems were still active in some locations, but were operating intermittently and in a state of disrepair – a factor that generated <mark>extremely volatile weather conditions</mark>. <mark>Some indigenous [if it can be called that] fauna may have survived the event</mark>, but RCTs were strictly advised to avoid all <mark>potentially hostile life forms.</mark>
After 8.4 days, all contact with RCTs was severed. Only one [RCT-06] returned, suffering extensive casualties.
In the teaser we see the “volatile weather conditions” the severe wind and “Indigenous fauna” being that Seeker/War Sphinx/Sentinel machine.
As the Absolute Record is on the Ark, this gives a reason for not only John to be there searching for Bias, but whoever ends up with the Janus Key will also want to get there. As to weather UNSC or Jul/Halsey have the key (or even if the two halves will be reunited in Escalation, only time will tell.
There is evidence that the Absolute Record is on the Ark. way back in Halo 3’s terminals:
"“Warning: Your intrusion has been logged.
04-343 (errant): Excuse me?
Your intrusion has been logged. And now it has been halted.
04-343 (errant): On whose authority?
Advice: Any further attempt to access [insects under stones] will result in your immediate addition to the local Sentinels’ targeting ledger.
04-343 (errant): Vexation! I am the Monitor of–
Judgment: Your authority means nothing here.
04-343 (errant): Impatience!
<mark>04-343 (errant): I have told you who I am. Who are you?</mark>
<mark>All our makers once held dear.</mark>
<mark>[Alexandria before the Fire].</mark>
04-343 (errant): Sincere apology. But how–
<mark>Explanation: This facility is host to the [Librarian’s] final–</mark>
<mark>04-343 (errant): The archive is intact?! Then our makers’ plan–[/SPOILER]Not only is the reference to the greatest ancient library “Alexandria” comparable to an “Absolute Record” but also what Spark says about “The Archive” and “our makers’ plan” “The Archive” is another reference to what 343 calls “The Absolute Record.” And “our makers’ plan” was the Librarians plan to have humanity awaken the Didact and have him give us the Janus key. But that plan obviously failed, as the Didact is still insane.</mark>
<mark> </mark>
<mark>What does this all mean for Halo 5’s story? Well, I have a funny feeling that the result of the Janus Key conflict in escalation will leave Halsey and Jul with both Halves. They will then head to the Ark. The UNSC Infinity will follow them there with John and Blue team aboard.</mark>
<mark>Something will happen where John will disobey an order, leaving him stranded on the Ark with or without Blue Team. here he’ll fight the hostile “fauna” in an effort to find Bias. Things will get really interesting when the UNSC and Covenant show up. The Covenant will bring Halsey and the Janus Key (reasoning above) and there will be a large 2-3 way battle on the Ark.</mark>
<mark>How does Agent Locke and Thel fit into all this? Locke’s goal is to track down John. He’ll be going from place to place trying to dig up clues as to John’s wearabouts.He may be the one that discovers John is on the ark. He tells Osman and Hood who then send Infinity to find John.</mark>
<mark>anyway, that’s just how I think it will all go down. of course with Escalation the pre-Halo 5 story is constantly evolving so we shall see if any of this comes to pass.</mark>