Roma LVIII was one of many Known Worlds where the Roman Empire never fell. There, Constantine worshipped Christ, who led him into victory in battle; Christianity became the official religion, and no other faiths were tolerated.
When Marcus Americanius Scriptor first visited Roma LVIII, Emperor Flavius Venerarius was the absolute ruler. A different version of Flavius Venerarius reigned in Roma CI, which was alike in all ways except that Constantine worshiped Mithras. (PROSE: Warlords of Utopia)