Distant from the traditional heartlands of civilization, the Yensai is the longest river in the known world, though the River Einan is nearly as long, and some other known rivers such as the River Eskana flow far away and out of the knowledge of most civilizations. The Yensai arises in the mountains of Dziltocampal, from which it winds north through the rainforests of the Laitra Empire, now incorporated into the vast Vithanama Empire, and onto the great savannah in territories in recent history ruled by the Hai Vithana and the Holy Moti Empire. It is known as the bringer of life, its banks lined with trees and beasts of great variety. It is here that the tribal Uggor rose to become one of the most powerful peoples in the world. The ancient city of Krato lies in its delta as it empties into the Galas Sea.

The most prominent tributary is known as the Scara Yensai (or "Black Yensai" in the tongue of the locals) -- flowing from the large Lake Ndeos until it merges with the main branch of the river.