Through the testimony of Ammianus Marcellinus, the essay investigates the persistent ambiguity of the Sacred in late antique paganism, as well as its undisputed vitality, even in a now advanced ‘age of anxiety’, in which the traditional religion of Rome lives on in the beliefs of the senatorial aristocracy, but also in the misplaced souls of simple people. Enriched and partly transformed by the fundamental contribution of Neo-Platonism, in the pages of Ammianus it is still capable of settling the destinies of Man.