The Republic of Vicisoria was founded as a trade colony of Sarmachia circa the 12th century BC. Originally a small post developed to exploit whales and valuable spices, the colony fell under the influence of Rephsis shortly after its history began.
Vicisoria was the birthplace of the Guild system that later spread to the rest of the Empire. Most of the governance of the province was originally led by the guilds, with each one having the ability to make their own laws (as long as these laws didn't conflict with a law of another guild, a problem that caused multiple long-running disputes and low-level conflict between them).
For seven hundred years Vicisoria was ruled by a hereditary council consisting of the leaders of the four (originally seven) biggest trading guilds and two representatives from the Naval Guilds that defended the province. Over time the wealth and power of the two guilds grew to equal that of all trading guilds combined, and after a quirk of inheritance led to the admirals of both becoming the same person he overthrew the council and led the province himself as its Admiral, with total approval from the Emperor, who retained the right to pick the Admiral's successor.
Vicisorian sailors were the first to discover the southern continent of Zeugitania, and the first to begin building colonies there. The five Zeugitanian provinces were known for their culture, which was strongly influenced by that of Vicisoria, which became prosperous from controlling trade and exerting influence over the southern provinces. However, it was dealt a major blow when famine struck the colonies and the cities started being harassed by barbarians from beyond the desert. After the imperial decision to abandon the five provinces, the remaining population was largely resettled in Vicisoria, giving the province's culture an exotic flavour.
The current Admiral of Vicisoria is Constantinus. It was his great-grandfather who finally began passing the reins of power from father to son, without consulting the Emperor in Rephsis. Constaninus's goal will be to continue this arrangement, and any hints of its end will not go down well. Descendants of Zeugitanian colonists also wish to attempt to restore control over the former colonies, although this is an expensive task that's almost certainly doomed to fail. Vicisoria, as an important naval power, is vital for the safety of the empire. If the Western Provinces fall to barbarians it will be open to attack, and this would be disastrous for your future as Emperor.