I believe that xur is an undead not like the guardians. This idea is only based on xurs ramblings. Xur simetimes says " the cells of this body are dying already" "Bodies come and go but the cells remember and if they forget the nine will remember" Some of the cells of this body began here it is strange to return". This leads me believe that xur does not have a body if his own. He must constantly find another body for him because the one he is in is dying. He may have lost his body some time ago and he must use other's. I also have a speculation that xur may be an old warlock or using the body of one. The only reason this came to mind was because of his arm band. So tell me what u think. Expand on the theory. If my grammar is off sorry.