these men are servants of the machine cult known as the adeptus mechanicus in warhammer 40k. they fix the imperiums machenes and gadgets and thier nickname is 'cogboys'. they sometimes give up part of thier body to be replaced with augmentics to become closer to the machine god.
i tried to re-create a techpriest in a white robe withe the telltale servo arm on his back.
plese rate and comment!!