Is a secret Chapter made up of Marines seconded from the other Chapters. Is the Space Marine equivalent of the Men in Black: the best of the best of the Chapters’ alien slayers. Is partnered with the Inquisition but is not beholden to it (and vice versa).
Are complete, self-sufficient, self-contained interstellar fighting forces. Are composed of around one thousand Space Marines each, plus many more serfs. Each have their own unique character and livery.
Are power-armoured supersoldiers. Are warrior-monks raised from pre-pubescence to execute the toughest lightning-strike missions. Venerate The Emperor as the greatest, most powerful human being ever to live, but not as a god.