If I get anything wrong, I apologize. And help me by giving me the correct info. And i had no clue what to write for their culture and society _-_
-Nation name: Black Marsh
-History (focus on the years 4E 201 to 205, anything before that is pr-established canon): Black Marsh has been able to remain independent while some of the provinces like Valenwood have been under the Aldermeri Dominion's thumb since the Great War. Beem-Teeus and Aney-Mei currently rule Black Marsh while making sure that they are well informed about the recent war and rumors of someone summoning the undead. 
-Leadership (type of government, leader, political agenda): Monarchy, with Beem-Teeus as the current king.
-Allegiance: None at the moment
-Military: The Shadowscales and An-Xileel
-Culture/society: Not much is known since the beginning of the fourth era, but it is suggested that they have an organized government. Their culture centers around the Hist with Sithis being considered the creator. Argonians do not share much about their culture with non-citizens of Black Marsh except for things like how someone would propose to a lover with a unique wedding band.