The Carthodox was a militarized religion, monotheistic and procreative. They came into conflict with the Necromonger Empire during its Fourth Regime.
The Carthordox came into conflict during the Fourth Regime of the Necromonger Empire, under Lord Marshal, Baylock the Brutal. The two religions crossed paths while trying to convert the worlds of the Neibaum System; the worlds becoming a holy battlefield.
An interesting, though probably an irrelevant footnote to the history of this particular conflict: there are suggestions purposed through oral history, that the Elemental race was advising the Carthodox in the course of this war. But many doubt this, citing the traditional neutrality of all Elementals.