River of Souls is a short story published in an anthology entitled Unfettered.

History

"Lacking health insurance and diagnosed with Hogdkin's lymphoma in 2011, Shawn [Speakman] quickly accrued a massive medical debt that he did not have the ability to pay. That's when New York Times best-selling author Terry Brooks offered to donate a short story Shawn could sell toward alleviating those bills—and suggested Shawn ask the same of his other friends."

—Release from Grim Oaks Press, the publisher of Unfettered.

Brandon Sanderson confirmed that River of Souls will include several scenes that were written for A Memory of Light, but were cut for various reasons. A video and transcript can be found here. These scenes are from the perspective of Demandred while in Shara.

Unfettered was released in June, 2013, after A Memory of Light.