[@Flagg] I was thinking that the sacrifice of warriors would be preferred for soulsteel, as some of their essence is embedded in the weapon. The user could call upon the prowess of said warrior in battle, making them stronger, giving them the wisdom of of fallen generals or the knowledge of enemies. Soulsteel weapons with the essence of long-dead heroes would be especially prized, maybe hereditary. Maybe it'd even be an honor for an esteemed commander to 'donate' himself to a blade at his time of death.