This is what I posted on another forum:
I believe 343 is clearly talking about the Didact. His lover, the Librarian, found all life precious, and while the Didact probably believes the same, he does have a duty to activate the installations if there is a flood threat which we all know there is again. The conflict in Halo 4 may lie there, Chiefs efforts to keep the installations from firing are contrary to the Didacts duty. And the artwork depicting the Didacts War Sphinx looks awfully similar to the brief enemy we see at the end of the concept art trailer, so there are an okay amount of signs pointing to Bornstellar being the enemy. As for the Legendary planet, I'm pretty convinced it's The Domain. In Terminal 2, as 343 begins mentioning The Domain, a clear picture of the legendary planet is shown. Also, the message at the end of the terminal is translated as Halo 4in Forunner script, a pretty clear indicator that that's the terminal to analyze. Back to the enemy, the precursors may be present as well, it is revealed that The Timeless One is devising some diabolical scheme which will be explained in Primordium. And about the prometheans, they were just the highest class of the Warrior/servant rate, which the Didact was part of.
