As a child, Cummascach lived in an abusive household, suffering regular violence at the hands of his brothers while his parents were unaware. Seeking to escape, he often fantasized about how if Connacht's fogs were thick enough, he could truly disappear and become a real ghost. One day, Cummascach was running from his brothers and stumbled upon an elderly druid who was conjuring fog through boiling vats. From this interaction, Cummascach and the elderly druid began a friendship as the elder druid taught Cummascach the ways of the druids and the elements around them.
Gradually, Cummascach tested his conjuring of the fog to an extreme level and soon used this technique to drive his own brothers insane, which caught the attention of the Children of Danu. Accepting the cult's invitation, Cummascach attained the title of High Druid and could soon made a fog grand enough to maintain the cult's secrecy.
The Viking jarlskona Eivor Varinsdottir of the Raven Clan came across the cryptonym of "The Ash" when she assassinated The Wren and recovered clues from her personal effects. After recovering The Wren's amber shard and giving to Deirdre Na Linni to make the antidote for Flann's poisoned army, Eivor decided to search for The Cursed's cottage in Tuam. Before Eivor left, Deirdre asked for her aid in tracking down and eliminating the Children of Danu, and Eivor agreed to help.
From The Wren's clue about The Ash, Eivor traveled to search a druidic ritual site on a hill between Lough Rea and Lough Tuam, in the middle of Connacht. Upon her arrival, Eivor looked around the abandoned ritual site and found another clue on a rock filled with human skulls. This led Eivor to explore Kiltober, a place southeast of Rathcroghan. There, Eivor noticed that the area was engulfed with druid warriors of the Children of Danu. Nevertheless, Eivor looked around and found the next clue within a tent of the area. The clue revealed the identity of The Ash, Cummascach, and noted that he was known to frequent the mines of Kesh Corann in upper Connacht.
Knowing where to go, Eivor traveled to Kesh Corann to find Cummascach and saw it guarded by the Children of Danu. Upon entering the mines, Eivor ventured through the cavern and configured herself through slips and cracks to find The Ash. Going through the right openings, Eivor found Cummascach and a fellow druid warrior conversing before they noticed Eivor. Upon noticing Eivor's presence, Cummascach and his fellow acolyte fought the jarlskona, but Eivor proved victorious and killed both Cummascach and his acolyte. Upon Cummascach's death, Eivor retrieved his amber shard and a clue about the member known as "The Blaze."