So far we’ve seen in this weeks bulletin that some of the Prometheans were left behind to protect something.
Also In the campaign trailer we hear cortana shout “I will not allow you to leave this planet!”
Also we know the covenant have something to do on this planet.
My question is what is it that ties these together. There must be something that the covenant are looking for and cortana desperately wants. There also must be something that the Prometheans are guarding.
I don’t read the books so I don’t know if there is any relevant information in them but what do you think this “ancient evil” or any of these factions want?
great question, seeking answers as well
I don’t know, maybe they’ll show us… I don’t know… in the game maybe? Why ruin a good surprise people?
My guess is, and this is just a wild theory, that this “ancient evil” wants something that can only be located on requiem and is going to try to use the chief to gain it. It could be why you hear the voice saying “I’ve long awaited this day reclaimer” (or something to that effect) at the end of the trailer. Again I don’t have too much info on the mythos of Halo and I’ve heard it is the Didact symbol and he is not our enemy. However in the same trailer we see the symbol turn upside down which can mean its someone else perhaps?
> I don’t know, maybe they’ll show us… I don’t know… in the game maybe? Why ruin a good surprise people?
Its merely a means of getting people to think of not “what is this enemy” , and “where do they come from”, but the more important “what do they want”, and “why do they want it”
Personally, I think its a Quarantine zone:
Since the Covenant and UNSC forces have found this place, the defense AIs are programmed to keep them from leaving, and possibly tell others of its location.
If this place is a safe zone, it would be best to keep others from telling where it is so that it doesn’t become a danger zone. Makes alot of sense. 
From the looks of it, they all need the Didact. From what I’ve heard, the “Covenant” believe one of their gods is on Requiem. This is confirmed with the Cryptum flying around. Ultimately, Chief is going to have to open it since humans CAN be a key to opening them. Perhaps the Didact is being held prisoner inside the Cryptum by the ancient evil and he’s looking for a way out?
The books do shed light on many things. I’ve read Fall of Reach, The Flood (Most of it), Ghosts of Onyx (Half of it), Harvest:First Contact, The Cole Protocol and currently Im reading Cryptum which is part of the forerunner Saga. So far, Cryptum is the only one that I’ve read that sheds light on Halo 4-6. It discusses more about the forerunners and 343i said the Greg Bear will tie into the new trilogy. Also I believe the Karen travis novels should shed some light on whats happened since we went into cryosleep.
For a better understanding I would read Cryptum, Primordium, (the third book after it comes out) and possible Glasslands, thursday war (when it comes out) and whatever follows it. Its a lot of reading but you get a lot of details out of them.
As for how everything ties together, your guess is as good as mine. Currently, we have a small understanding on whats been going on since we went into cryosleep and we know almost nothing about the forerunners other than what the novels tell us…
Give it time my friend.
You should definitely read the books, it’ll help a lot with the story for the Reclaimer saga. 
OP: There are so many possibilities for Halo 4’s plot, it’s not even funny.
The Prometheans could be guarding something, for quarantine, etc.
We don’t know who Cortana is yelling at, or the circumstances.
The Covenant could be there for so many reasons.
So much speculation, but it’s fun to do.
> You should definitely read the books, it’ll help a lot with the story for the Reclaimer saga.
> OP: There are so many possibilities for Halo 4’s plot, it’s not even funny.
> The Prometheans could be guarding something, for quarantine, etc.
> We don’t know who Cortana is yelling at, or the circumstances.
> The Covenant could be there for so many reasons.
>
> So much speculation, but it’s fun to do.
aye