Nightmare is a mysterious knight, clad in dark azure armor, with his right arm mutated into a giant grotesque three-fingered claw as a result of his Malfestation. He is incredibly bloodthirsty and fanatically loyal to his cursed sword, Soul Edge. His body belonged to the noble knight Siegfried, whom Nightmare still retains some memories. Nightmare struggles with the knowledge of having murdered his own father as Siegfried. He also believes he can't be saved, unable to stop his bloodlust.