Nightmare was the alter-ego of Siegfried Schtauffen, a character in the Soul series of fighting games. His first appearance was in one of the possible endings for the Siegfried character in the game Soul Edge. In the sequel Soulcalibur, he was given a name and featured as a central character. Ever since then, Nightmare has been the main antagonist and owner of the Soul Edge, and thus the objective of most other characters in the story. Appearing in every game of the series, Nightmare has served as a recurring antagonist, and as Siegfried a recurring protagonist.