The Soulforged Ash is a symbol of their power-they can transform into it, grow from it (When Feanor was nearly killed, he spread his ash to a trooper and formed through him), and even attack with it. It also brings weaknesses, however, such as Feanor getting nearly killed by laser fire and Raistlin getting blown across Geonosis by Jedi Master Mundali. The ash contains extreme dark energy, and when a Soulforged is killed that is all that is left of him. Feanor became the second Soulforged by going to Rhen Var in an effort to see if he could find the Black tomb. He found a high concentration of ash near a broken and ruined temple, and it consumed him. The Soulforged supposedly ended when Acheron absorbed Feanor, but in a way, Acheron is the third Soulforged.