Let's say a setting contained a world like ours. Due to unfortunate circumstances, a large portal to hell opened up in the middle of the planet. Numerous demons spilled out into our reality, overthrowing governments and killing billions of people. These demon hordes were led by devil archons, who settled in various countries and ruled with an iron fist. These nations were essesenti ally turned into torture camps, where humans were enslaved and murdered for the amusement of their overlords.
The only surviving nation would be a powerful theocracy that managed to hold out against the demonic horde. A collection of priests had gained special abilities that are said to come from God. These abilities would be used to form a barrier that would prevent demons from crossing over into this nation. It would also be used to develop a form of "holy tech" that would be specifically developed to fight demons or banish them back to hell.
A religion would develop, centered around worshipping of the one true god. A high council of priests would actively maintain this barrier, while delegating the running of the church to other members. Religious and secular law would become one, with no separation between church and state. Other faiths would be declared heretical, and life would revolve around traditional values and ethics. People would be equal in the sense that they will be judged accordingly by God for their actions in life, but a social hierarchy would develop that individuals would be pressured to abide by and respect.
How can this country sustain it's theocracy while maintaining a limited form of democracy in this setting?