This image of comparative height of Spartan-II John-117 compared to Promethean automatons, shows silhouettes of all know types, however, what is the unknown end figure after the Promethean Knight? It is specified and rumored to be the Didact, Shadow-Of-Sundered-Star, in a more digital form… this poster was stated to not feature the Didact.
Then that’s The Warden Eternal, Keeper of the Domain.
http://www.343industries.org/forum/fileshare/gallery/album_723/sml_gallery_29485_723_61329.png
(This one could do with photoshopping for a drink).
http://www.343industries.org/forum/fileshare/gallery/album_723/sml_gallery_29485_723_164114.png
So the Ur-Didact may have accidentally reactivated The Domain…
Its not the Didact its the “Warrior Eternal, Keeper of the domain”