This valley is cut by the fast and winding Agallurân river. A vast marsh, Ulnirrêth, is at the southwestern edge of the valley. In the northern reaches of the valley are the Hagmoth hills.
In the Demon Spawn War, a great battle was fought here between demons under Aperoq and those serving under Chronos. One regiment-sized unit, the Vauquix, escaped the battle by all teleporting to a previously scouted location in the Underdark.
In later years of the Horgon Era, Imrabêl became territory of minotaurs tribes. By the third century of the First Epoch, they were a formidable force and a major problem for those seeking to pass through or open up trade. Around this time, the southern edge of the valley became territory of Khazarkar tribes, while the northern reaches were being claimed by the Tragarans. When the khazarkars built the settlement Chal-Kazod, the minotaurs banded together and warred with them. They claimed to peace makers that the Khazarkars were getting to close and effectively sealing off the south, while to the north the Tragarans were soon to do the same thing. The valley would see three wars over the next centuries. In the last of these, the Third Imrabêl War, the First Khazarkar Empire defeated and enslaved the minotaurs. Thereafter, the valley was slowly colonized as the Khazarkar territorial ambitions moved northward. Imrabêl became the breadbasket of the empire up until the Great Exodus (998 - 1017).
After the Gulimbor Cataclysm (996 - 1203), the valley returned to the wild with ruins like Chal-Kazod and Athânâlo, the latter a the former capital of the First Khazarkar Empire, becoming havens for magical beasts and monsters.