The Valkyries were a division within the Asgard military forces that served as a special ops group during combat operations. Based on the Norse myth, the ranks of the Valkyries appeared as Human females in order to distinguish them from the other Asgard and this image stuck with their Human charges. Their ranks consisted of Asgard that worked in group operations against enemy targets ranging from the Goa'uld to the Replicators. At one time, Tyr served as the commander of the Valkyries. (RPG: "Fantastic Frontiers: Stargate Season One")