Trebizand, from the word Trebizond
The Empire of Trebizond, founded in April 1204, was one of three Byzantine successor states of the Byzantine Empire. However, the creation of the Empire of Trebizond was not directly related to the capture of Constantinople by the Fourth Crusade, as it had broken away from the Byzantine Empire a few weeks prior to that event. (Good timing)
Geographically, the Empire of Trebizond never consisted of much more than the southern coast of the Black Sea. Its demographic legacy endured for several centuries after the Ottoman conquest in 1461, and a substantial number of Greek Orthodox inhabitants (called Pontic Greeks) remained in the area until the early 20th century.
At that time, the remainder of Orthodox Christian inhabitants in the area were deported to Greece (starting in 1923), as determined by the Population exchange between Greece and Turkey. This agreement did not include local Muslims who spoke Greek dialects, who live in the Trebizond area to the present day.
And Kuro, I have heard of the Kievan Rus, and the Nords are based on the Norwegian Vikings (Norse, Nords), Not the Rus, who were formed by the Varangians, different Vikings then the Norse. I meant Norse Vikings never clashed with Mongols, If I had meant the Kiev Rus I would have said "The Kiev Rus never clashed with Mongol Warriors" which they did. Secondly the Italian city states are Milan, Genoa, Venice, Florence, Pisa, Naples, etc. When they got rid of Feudalism after the Bubonic Plague (Black Death), they slowly got rid of the Nobility, being replaced with Merchants, until the city states were eventually taken by Despots, not elected leaders, the most famous case being the Medici family of Florence. Much like how the Rhodoks (The Italian City States) rebelled against the Swadians (Based off of France, Germany and England, some of the countries most deeply entrenched with Feudalism).
Calardia is separated for the most part, but not entirely, there are still some passes open. In Warband they have left more of the map open, the Sarranid desert, for example. Also it is possible other empires could come exploring from beyond the Western Boarder of Calardia, they could set up outposts west of Swadia and the Nords, or even to the east of the Vaegirs, there is still room in that area of the Warband map for a city or two.