DOOM ETERNAL: LORE - ORIGINS OF THE DOOM GUY - WHO IS THE SERAPHIM? - SENTINEL HISTORY - DOOM 64

"After playing Doom Eternal, I am really beginning to believe that Samuel Hayden is actually Samur Makyr. The reason I think that is that in Doom Eternal Samuel knew so much about Urdak to the point that he would have had to be there at some point for a fair amount of time. The other reason is that Samuel had extensive knowledge of Nekravol along with the Argent factory there." - from FuedOfJustice