Drenvun is the longest sunken wetland rift of Midrêth. Much of the bottom of this area is covered in deep forests, tangled swamps, lakes, ponds and broken ground. It begins near the southern edge of the Nalêth desert and the Damreth mountains. The streams and rivulets coming down the Damreth highlands form the headwaters of Drenvun. These sunken lands are also fed by the many swamps along the Dargirth river and periodic flooding, particularly during the Ice Cap Melt. Going south into Miradelgûn there are floating settlements on shambog and many villages on stilts. These place are home to humanoids favoring the swampy conditions of the area, lizardfolk, trolls, and the bullywug. Near the southern edge of the Rôzadruk forest, the sunken lands of Drenvun cut east into sector Halmarth and ends at Hullbreaker Bay.
Drenvun's northern areas have many tunnels leading into Chaexidor. A mile or so down from these is the kuo-toan empire Âkhi. Raiders out of this empire traffic these tunnels frequently, debauching on the surface to snatch food and loot.