The main object of this article is Latin Christian historiography in the epoch of transition from the Early to the Late Empire, lifetime of Constantine the Great (272-337). At that time it begins to form as source of political ideology. Exactly from this moment representation of Emperor’s power takes more place in texts, written by Christian authors, than traditional themes, such as polemic with pagans, discussion about theological questions, philosophical problems etc. In this work opus by Lucius Firmianus Lactantius ‘On the Deaths of Persecutors’ (De mortibus persecutorum), written in that period, is studied as an imortant monument, that fixed evolution of the power’s images in literature and, particlarly, in historiography of Late Antiquity.