The article below is just a basic introduction to the topic. For something more advanced, written by pros and a fantastic leveling guide, my recommendation would be this Elder Scrolls Online Leveling Guide. I could not find any other guide that comes even close in terms of the impact it had on me.
One of the revealed regions within the region is called Shadowfen. The land is controlled by the Ebonheart Pact and lead by Jorunn the Skald-King. It is located in the north-western region of the Black Marsh that borders with Morrowind. It also includes the ancient city of Stormhold.
Hailing from this region are the Argonians.