Middle Argonia is a far-off region found in the province of Black Marsh, specifically in the center of the area. It wields a wide-spread reputation as the impenetrable center, and the dark heart of Black Marsh, where only the Argonians can survive. The city of Helstrom is found here. The marsh is very dense, and it contains Helstrom Heart-Mud, which is known for being really black. The province is known for various river systems, all of which flow into Middle Argonia, one such example is the Onkobra River, found near the city of Gideon and the region of Shadowfen.
The Hist of Black Marsh are known to grow in the innermost region of the province, and so because of this, there are several tribes found exclusively in Middle Argonia. One of these tribes are the Agacephs, a needle-faced variant that comes in many bright colors. Others include the Paatru, a toad-like variant, the Sarpa, a winged-variant, and the Nagas, a warrior-tribe that resemble adders, though they can also be found in Murkmire. In 1E 2811, the Imperial Legion of the Second Empire invaded Black Marsh in the historical Battle of Argonia. The last of the Argonian resistance was defeated by the Empire and were forced to retreat into Middle Argonia and the city of Helstrom. Here, they were able to avoid the Empire, as their siege weapons were unable to traverse the dense marsh. However, it was at the rest of Argonia's expense, which was subsequently conquered in the Blackwater War.
- Field Guide to River Trolls — Phrastus of Elinhir
- The Argonian Account, Book 3 — Waughin Jarth
- Pocket Guide to the Empire, 3rd Edition: The War with the Trees: Argonia and the Black Marsh — Imperial Geographical Society, 3E 432
- Stormhold, City of Shadowfen — Cirantille
- Neelo's Notes — Neelo
- Onkobra Kwama Mine delve in ESO
- The Argonian Account, Book 4 — Waughin Jarth
- The Blackwater War — Valenca Arvina, Historian-in-Residence at Gwylim University