The Religious War began with the Order of Light firing the first nuke at a city whose entire population served the God of Shadows, Zenith. An entire city of thousands was obliterated.
A cannon magic circle was the source of the attack.
This act triggered immense tension between the two religions. The worshippers of Zenith became enraged when they learned of the city's destruction, and hatred was born.
Since the Order of Light had openly declared war against the Church of Zenith, the followers of Zenith began preparing for war against their enemies.
The destruction of the city reached the ears of the Prophetess. As crowds gathered at the temple to hear the words of the Shadow Holy Book, their hearts were already filled with hatred and a thirst for war.
But as mere mortals, they sought guidance.