I believe Kbar is Xur because he killed a gorgon and used it's remains and his light to create the relic because he knew he was going to die as he saw his whole strike team die one by one so he used his light to create the relic under the assumption he was going to die but no he didn't he lost his light and became a creature of the darkness (Xur) so he comes back every week to help guardians finish what he started and as Kabr says "If I speak again, I am not Kabr"