I have a couple theories about the Warden Eternal I figured I’d drop and see what you all think.
1st Theory- This one is more plausible in the sense that it brings up Haruspis.
So, as I mentioned in another post, Haruspis was essentially implied to be a living conduit to the Domain, almost a direct representative for it. Haruspis was also referenced as being similar to Catalog in that there may have been more than one but they were thought of as one entity and that he/she/it may have been partially or completely technological with a forerunner personality.
That being said, Haruspis was essentially the gatekeeper, or Warden, of the domain. The only part of this theory I don’t like is that there is no reference of whether Haruspis was extremely combat capable as the Warden Eternal is so obviously. Which leads me to theory 2.
2nd Theory- Endurance of Will. Endurance was composed on Requiem, and all we see is Knights on Requiem. But why would the UrDidact make only Knights? What if the Domain itself, or maybe Haruspis (still essentially the Domain,just it’s “hands”) entered Requiem after the Librarian left and aquire a new tool, with the requisite skills to act as a more formidable Warden and in the process, aquired the forces necessary to prepare itself for its eventuality of using/helping/testing the Chief. Remember, the Librarian had planned for the eventuality of the MC and the Domain, though silent during the twilight of the Forerunners, likely kept tabs on what was going on and would have known what the Librarian was doing, either while she was doing it or after her death…this one seems to stretch a bit though.
Either way, I expect the Domain is going to play a fair part in Halo 5, and I can’t wait to see what it wants.