Religious event
As Ereshi the Crow's work grew more complicated, she eventually allowed her most devout followers to assist her. She taught each of them how to gather and collect souls so that they could go across the lands and bring souls to her, preventing the creation of Demons. These disciples were later known as The Black Parade for the dark but neccesary nature of their work.
With their aid, Ereshi never left Eresh'Ak and was able to cleanse souls more effectively.