Nightmare appears in every game of the series .
Nightmare has served as a recurring antagonist in contrast to the protagonist role played by Siegfried , as well as serving as Siegfried 's archenemy until Soulcalibur V where a new Nightmare was there .
Appearing in every game of the series , Nightmare has served as a recurring antagonist in contrast to the protagonist role played by Siegfried , as well as serving as Siegfried 's archenemy until Soulcalibur V where a new Nightmare was there .