Idân is a valley northeast of Erchinor. It begins near the Core Sea and goes northeast into Steirgar. The valley has many streams which drain into the Core Sea to the west.

In the Cinazan Front, a major battle was fought here between the Khazarkar Empire and the Flux Pact. The prolonged presence of the Horde of Chaos in this valley caused the land and water to be warped by the chaotic energies and turning it into a chaos ruin. Hills are misshaped, boulders are twisted into unnatural shapes and some streams are discolored or smoke with a putrid or pleasing odor.