Shadow Moon may refer to any the following characters.
Despite their father trying his best to save both from Gorgom, only Kohtaro successfully escaped. Nobuhiko instead was heavily injured in the process and fell into a deep coma, under Gorgom's clutches. Later on in the series, the three high priests of Gorgom used their combined powers to forcibly reawaken Nobuhiko from his coma, at the cost of retaining their humanoid forms. Nobuhiko, having his mind altered alongside his body, was now Shadow Moon.
Like Kamen Rider Black, Shadow Moon utilizes the Kingstone to transform and is armed with the Satansaber, a sword crafted specifically to be used by the Century Kings.
Century King Shadow Moon is Nobuhiko's alter-ego after being brainwashed by Gorgom. Shadow Moon has roughly the same amount of power and strength as Kamen Rider Black. His primary techniques are the Shadow Punch and the Shadow Kick.