The great jungle swamp of Gurutharni is near the heart of eastern Ma'Ohari. Gurutharni has foliage so dense that if it were not for the innumerable rivulets, streams, and deep pools, you would think you were crossing a jungle. Land travel through Gurutharni requires getting your feet wet. The dry areas of Gurutharni are probably less than 10% of the total area. The jungle's trees and other foliage are all of a variety that thrive in humidity and perpetual wetness. In some areas the foliage is so dense that an area crossed may be a vegetation bridge covering a deep pond.
Gurutharni is a hot and very humid wetland with hundreds of geysers and countless geothermal streams. It wasn't always like this though. During the last three centuries of the Lith-Crillion Era, the empire Tilnangau controlled this area and lands all the way to the walls of Mughakh-Gol. Back then, the swamp was only 30% of the size it is today. The empire frequently battled with the Vedrii and yuan-ti lurking in the western and southern waterways of Ralban.
Gurutharni and a large part of eastern Ma'Ohari were changed during the waning years of Varelay. This demon-led empire undertook massive mining operations east of Mughakh-Gol. Varelay enslaved Tragarans, Vedrii, yuan-ti, fire giants, chaos archons, and anyone they could get their hands on. Their mining was so environmentally destructive that they ended up changing the eruption cycles of a group of three volcanoes, collectively known as Hen'khas. The increased activity of these volcanoes caused earthquakes, ash storms, lava flows, and a lot of environmental damage on the surface and below. Styming became a lake during this time. Tilnangau's cities began to sink during this time, and long periods of intense heat and toxic gases kept many trapped indoors. The people of Tilnangau splintered with some choosing to stay on the surface and others to go into the depths with their crumbling empire. Those that went into the deeps became kuo-toans - transformed into humanoid amphibians by their god Blibdoolpoolp. Those that stayed on the surface had to face the violent eruptions and earthquakes of the Varelay Upheaval (2608 LE - 16 HE) or flee to other lands. Most of the Tragarans chose the latter, migrating far south into Gulimbor.
In the early part of the Horgon Era, the volcanic activity coming out of areas like Cerbere and Malephar settled down. As a result, the Vedrii and yuan-ti started taking back the area. They fought over the land and spoils left behind by the Tilnangau.
In the centuries after Tilnangau disappeared into the Underdark, many petty empires have come and gone. The most lasting empire has only recently formed with the yuan-ti empire Malshirk'iss.
Gurutharni is the abode of yuan-ti, Vedrii, naga, hydras, black dragons, and many other horrors. The swamp is fed by the mountain streams from Glamvir and the daily rains that soak Ma'Ohari. When not flooding, the swamp drains south into a river called Ralban.