Omnia was a powerful and oppressive theocracy until about a hundred years before the present. It is ruled by the Cenobiarch (the Superior Iam) who is the head of the Omnian Church. He has 6 Arch Priests, 30 lesser Iams and a numerous other clergy to assist him and governs from the Citadel in the capital city of Kom (a cross between Jerusalem and the Vatican, though its name is probably derived from Qom).
The Omnian Church and religion arose out of a book called the Book of Om and was originally an intolerant religion. The country was known for its empire building, as it conquered neighbouring countries on the continent of Klatch in the name of the Great God Om (similar to the interpretation of the Crusades). The Omnian Quisition, like the Catholic Church's Inquisition was a state secret police run by deacons, which tortured and executed 'deviant' Omnian citizens in His name. In fact, most things good or evil were done in His name. Peddlers used to sell dubious religious artifacts in His name and His name became an excuse for any kind of dubious activity. When it was about time for the Eighth Prophet of Omnianism to appear, many members of the Omnian government and military had in fact joined a secret anti-Omnianism movement. The proceedings and outcome of this movement are detailed in Small Gods and ultimately led to the Eighth Prophet, Brutha, becoming the Cenobiarch, at which point the country reversed directions and became the home of a renowned theological college and library. Brutha had brought all that he could memorize of the books in the Library of Ephebe back to Omnia, set them down in writing again, and opened the new Omnian library to all citizens and philosophers, including foreigners. Half of the Ephebian Philosophers now live in the Omnian library and the country is renown for the constant arguing among the clergy, as new interpretations of Brutha's teachings spring up every day.
Omnia now exports many evangelical preachers, some of them are priests, but many of them are ordinary citizens. People of other countries still do not like Omnians in general. Those who have not kept up with the times think that Omnians still set fire to non-Omnians (see Carpe Jugulum). While those who have kept up with the times are fed up with getting a pamphlet every day from their Omnian-immigrant neighbour (see the article on an exemplary emigrant, Visit-The-Infidel-With-Explanatory-Pamphlets who currently lives in Ankh-Morpork). The currency of Omnia is the obol.