River of Souls
River of Souls is a short story detailing how Demandred acquired the second part of Sakarnen and fulfilled the Sharan prophecy of the Wyld that was written for A Memory of Light. It is considered mostly canon, though certain elements of world building were not checked so should not necessarily be considered as such (this is mentioned in the Intro to River of Souls, written by Brandon Sanderson).
Plot
Demandred is alone in the Oneness when Mintel arrives unexpectedly, having ridden the caprisha through the City of Dreams, which Demandred considers dangerous. Mintel tells him he is there to see angor'lot, the True Destiny and the Crowning of the Wyld. They head together to Abyrward where they encounter Shendla and Torn. Shendla tells him he has come to save them, free them from fate and make them their own people again. He tells her he will protect the people if he can.
He enters the cavern where he is surprised to find plants blooming and assumes the Guardian must be one of the Nym. He channels, sending fire at a vine, but instead of burning, it spreads more. He looks ahead and sees a mouth with needle sharp teeth with insect like arms and realizes it is a Jumara that transformed, but grew too large to get back out of the cavern. As he cannot use the Power against it directly, he channels to melt rock and throws the molten rock at it, forcing it back. He is able to drop onto it and kill it with his sword.
He heads further into the cavern, coming to a place where the plants have grown together into a face. It asks him if he has come to give it rest, saying it is no longer one of the Nym, and he kills it. The plants shrivel away, leaving what seems to be a cup, which he combines with a rod he had previously found. He walks out of the cavern announcing to Shendla and the Ayyad that he names himself the Wyld and Dragonslayer.
He thinks how it has taken him two years, from posing as a slave to accidentally leading a revolution, but that now he has the power to destroy Lews Therin.
How It Came to Be
River of Souls was published in the "Unfettered" anthology. Shawn Speakman approached Brandon Sanderson about including something in this anthology, and after confering with Harriet, it was decided that these deleted scenes from A Memory of Light, should be submitted. Brandon Sanderson on River of Souls.
The scenes were finally cut from the book, after they were deemed too distracting from the overall theme of the Last Battle and introduced several new questions at a time when it was more important to wrap up story lines.