Erebus

Also known as "The Watcher", Erebus is a mysterious figure Group Alpha encountered in the town of Vohnenheim. Living on the cliff face and said to have been there as long as the citizens can remember, he wears a strange mask and has great knowledge of The Ash Wastes.
After agreeing to guide Group Alpha through The Ash Wastes in exchange for help defeating a behemoth Flail Snail, Group Alpha realized that Erebus was in fact a Formis Mark 3 once he integrated the shell of the snail. He has no memory of his past , only that he was awoken a hundred years ago and told he would be needed for a great battle that is to come.