I am a little confused about the Didact, namely which one we are facing? (See spoiler below)
[color=’#151515’]So the original Didact was supposedly killed by the Master Builder when he ordered the firing of one of the Halo rings. His form and personality lived on in Bornstellar, who, for all intents and purposes, became the Didact. This occurred before the sterilization of the galaxy, but after the devolution of humanity.
We also know that, in the midst of the Forerunner-Flood war, the Didact (one of them, at least) used the Composer to create new Prometheans from the degraded humans, which the Librarian did not take kindly to. She therefore shot him and had him imprisoned within the Cryptum we see on Requiem.
Now, it seems that the two events described above must take place chronologically in order for the entire story to make sense. But the Didact is ultimately the one to fire the Halo rings. One of them was supposedly killed, facilitating the continued evolution of Bornstellar into the Didact. And the second was supposedly imprisoned before the firing after inexplicably doing some really fucked up things to the humans (who he, Bornstellar that is, originally had a soft spot for).
I guess the question here is then which Didact do we face in Halo 4? The original who maybe didn’t die and came back to continue his experimentation? Bornstellar who came to resent humanity as much as the original? Or perhaps a third incarnation?