User blog comment:Schiffy/BG9: Man, Machine, or Something Else Entirely?/@comment-5592530-20130925132937/@comment-11051098-20130925172419

Maybe BG9 was a human once, and suffered serious injuries in an explosion following a battle, and Yhwach got him rebuilt with mechanical parts that included partly or totally rebuilding his head, so that he has no memory of his former life, and as far as he know, "never breathed".