I believe that this NPC is in fact a Warrior Guildmaster, since when I used sneak behind him he told me to begon since I was not of the Warrior Class.
Killing him resulted in the following faction changes:-
Shoulders of Seru got worse
Heart of Seru got better
Eye of Seru got better
Seru got worse
Katta Castellum Citizens got better
Nathyn Illuminious got better
He didn't drop any items when killed.