Before the Didact was blasted off by a grenade, he activated the Composer and unleashed its deadly power on New Phoenix.
When charging it up, a slipspace event occured under the Composer as stated by Cortana in Midnight:
> Cortana: “Activity! Significant slipspace event, building under the Composer.”
> John-117: “He’s powering it up.”
The Didact fell into that slipspace event whether still alive or not.
Now when watching Spartan Ops - Episode 5: Memento Mori, we can see that Doctor Halsey activates the soul of a Promethean Knight:
> Roland: “Doc, this things looks … kinda familiar!”
> Halsey: “Yes, it’s very similar to an AI matrix. But we expected that.”
(I love when she is blown away by that pulse. Made me lough)
> Halsey: “Roland! Freeze all monitors!”
> …
> Halsey: “Not pictures! Memories! An alien AI full of human memories!”
> Thorne: “That’s New Phoenix. I grew up there.”
> …
> Lasky: “The UNSC is aware that Prometheans are ancient humans.”
> Halsey: “That is not ancient; that is the attack on Earth from six months ago!”
> Thorne turns towards a picture of the artifact the Spartans retrieved from Requiem.
> Thorne: “You knew.”
> Lasky: “This isn’t possible! I have no idea how all these memories got from Earth to here!”
> …
> Halsey turns towards the screen Thorne was looking at.
> Lasky: “What is it, Doctor?”
> Lasky views the screen and the artifact on it.
So we know New Phoenix was utterly composed by the Didact. Both the artifact and the human memories were somehow transferred to Requiem. And there was no Covenant on Earth to do so.
I suspect that the Didact launched the artifact, landed it on Earth. Then he activated the slipspace portal to Requiem. He started the Composer and send all the human souls to Requiem. Do you remember that he built his first Promethean army composed of humans on Requiem as well? (As seen in the sixth Domain Terminal video.) So I suppose that his Promethean Production Facility is also located on Requiem.
Now that figured out, we can come back to the subject of this thread. If the slipspace portal inside the Mantle’s Approach really led to Requiem and teleported the human souls and the artifact there, then the Didact, whether dead or alive, might also have been teleported back to Requiem when he fell into the slipspace event after his defeat.
Do you agree?