Argonnessen is a continent as large as Khorvaire but almost totally unexplored for two reasons. Firstly, it is very difficult to reach Argonnessen due to bizarre currents and treacherous reefs. Secondly, Argonnessen is populated almost entirely by dragons.
Little else is known about Argonnessen, save that very few explorers have returned to tell the tale of their doomed expeditions to the interior of the continent. One thing that is known for sure is that there are tribes of savages known as the Seren Barbarians who live mostly on the isle of Seren just off the coast. These barbarians worship the dragons as their gods, though the dragonborn tribes on the isle believe the dragons to be their kings and ancestors instead, or possibly as well. Either way, the human or dragonborn Seren tribes both brutally defend the mainland shore of Argonnessen against travelers.