"Never before had we encountered a race with powers that rivaled our own. Never did we imagine that the sins our past would come to haunt us again. In our overconfidence, we were unprepared and outnumbered." - Melia

The Ancients once ruled the Milky Way until they created the instruments of their downfall: Mankind and the Forerunners. They revolted and claimed the galaxy. Now their Revenge is ravaging their killers, and the children will soon meet their creators.

The war is over, but the Spartans don't know that. Desperate to find a way back into the fight, they inadvertantly stumble across ancient devices, and an alliance so old that no one remembered it ever existed.