Narben is a death-sword and one of the Dread Trove.
Narben's powers are said to be not like the savior's light of Gwydion but far darker, of death. Narben is said to be powerful enough to have given the King of Hybern victory over the second war on Prythian if he had had it, and able to slay monsters such as Lanthys.
Narben is said to be older than Gwydion.
Rumor claimed Amarantha found it somehow at some point, but it would not come to her hand nor the hands of any of her commanders, so being denied by it to possess its power, she dumped it into the sea out of anger rather than let the King of Hybern attain it. For this reason, Narben is believed to be lost, and possibly, destroyed.
When Nesta Archeron and Cassian visit the Prison they encounter Lanthys. He sees Nesta carrying Ataraxia, and tells her that he recognizes it is not Narben, Nesta however was not familiar with the name at that time.