I was rewatching the Halo 4 terminals today and I'm disappointed that pretty much none of it has been capitalized on. Sure, Halo: Silentium expanded on the Ur-Didact's madness, but ancient humanity is only alluded to with the Hellcat armor, we've yet to see the Librarian AI except for a brief appearance in Escalation, and the Librarian's hope for he Ur-Didact to teach humanity how to move past the Forerunners mistakes, barring continued Gravemind-induced madness, is likely a non-starter since he's only being kept around to possibly fill out Halo's rogues gallery of villains. Instead we get evil Cortana and Sir Friendzone. Wonderful.