Halo 4 video discusses the Return of the Forerunners
Halo 4's Promethean enemies are a badly kept secret indeed, but this developer diary is an 100% official authority on the matter.
Promethean assets have leaked a couple of times over the last few weeks; gamers are understandably pretty keen to check out the new enemy type ahead of halo 4's November release, exclusively on Xbox 360.
Visit Halo Waypoint to read more about the Forerunners and view some concept art.
Thanks, Joystiq.