: It was never confirmed or I think even hinted who it was. The last I knew (I
: want to say it was 2009) Marty still said no one had even guessed
: correctly who it was. I would think it couldn't be Mendicant Bias because
: whoever it is talks about walking the Earth for ages, which I would think
: couldn't have applied to MB, but there were story changes made between
: Halo 2 and Halo 3, so who knows. Then again, a lot of people theorized it
: was MB who said that, and as I said Marty said no one had figured it out,
: so unless he was lying, or he was unaware of the theories, it can't be MB,
: or for that matter a bunch of other characters.

Could it be Guilty Spark? We know that he was once human, and he could be referring to the Forerunners as Angels.