Apollo Geist

Geist (アポロガイスト) was the Chief of Security of G.O.D., assigned to execute any member of the organization no longer of use. Initally appearing as a man wearing a white tuxedo with black gloves until he invokes "Apollo Change" (アポロチェンジ), Apollo Geist's true form is an armored cyborg.

First destroyed following a failed attempt to take out X-Rider by shaking his explosive hand after he was defeated by X's X Finishing Kick, his husk was reconstructed at the Apollon Palace by two G.O.D. scientists and he became Revived Apollo Geist (再生アポロガイスト). As a final resort, he assumed the form of a giant fireball but was ultimately destroyed by X's X Kick.

Let's Go Kamen Riders
Due to a change in history caused by Ankh leaving an O Medal behind in the year 1971, Shocker achieved its goal of world dominion with the Shocker Greeed and new members from the various groups joined an alliance under Shocker's control. Apollo Geist, King Dark and the Government of Darkness were part of Shocker's alliance. He was never killed by X, not needing the Perfecter to sustain himself even years into the future. When the timeline was partially restored and the Riders returned, he tried to face X, only to be defeated. He was only destroyed, however, when the Great Leader became the Great Rock Leader and spread destruction around the world. This Apollo Geist used a modified version of the design of Decade's version, having the Perfecter removed, and also the actor of that same version voiced him, however, his official bio makes it clear that he's the original character, rather than Decade's version.

Monsters

 * Mighty Atlas (鉄腕アトラス Tetsuwan Atorasu, 8 & Movie) - An Atlas-themed seaweed monster. Destroyed by X Kick.
 * Mach Achilles (マッハアキレス Mahha Akiresu, 9, 10, 21, Movie & 28) - An Achilles-themed turtle monster. At first he is able to block X Kick attack and defeating Kamen Rider X with help from Apollo Geist by shooting him cause him injured which later falling to bottom of the river. Later after Kamen Rider X has done his deadly training with Tachibana Tobei by shooting him with Machine Gun. He is able by defeating Mach Archilles with his new moves. Destroyed by Apollo Geist after defeated by X Two-step Kick.
 * Flaming Prometheus (火焔プロメテス Kaen Purometesu, 10, 21 & Movie) - A Prometheus-themed hyena monster. Destroyed by X Kick.
 * Hydra (ヒュドラ Hyudora, 11 & Movie) - A Hydra-themed eel monster. Destroyed by X Kick.
 * Chimera (キマイラ Kimaira, 12, Movie & 27) - A Chimera-themed lion monster.
 * Ulysses (ユリシーズ Yurishīzu, 13, 21 & Movie) - A Ulysses-themed sea snake monster.
 * Reaper Chronos (死神クロノス Shinigami Kuronosu, 15, 16 & Movie) - A Chronos-themed ox monster.
 * Cerberus (ケルベロス Keruberosu, 16 & Movie) - A Cerberus monster.
 * Alseides (アルセイデス Aruseidesu, 17 & Movie) - An Alseides-themed root monster. Destroyed by X's Smash The Head move.
 * Cateus (キャッティウス Kyattiusu, 18 & Movie) - A Cadeus-themed black cat monster.
 * Ogle-Dagger (オカルトス Okarutosu, 19) - A Benjamin Ogle-themed mole monster.
 * Salamander-Gong (サラマンドラ Saramandora, 20 & 28) - A Lue Gim Gong-themed salamander monster.

Kamen Rider SD
Apollo Geist: A member of GranShocker. He was among the villains at the meeting with the Great Leader.

Kamen Rider SD: Sortie!! Rider Machines
Apollo Geist is the boss of the Desert Battle Stage. He uses his bike to try to outrun X and uses multiple Geist Cutters which move around on the road to attack X before returning to him.

Portrayal
In Kamen Rider X, Apollo Geist was portrayed by Yasuhiko Uchida (打田 康比古). In Kamen Rider Decade, his voice and his human form Guy are portrayed by Kazuhisa Kawahara (川原 和久), who also voiced Apollo Geist in OOO, Den-O, All Riders: Let's Go Kamen Riders. In his appearance in OOO, Den-O, All Riders: Let's Go Kamen Riders, his suit actor is Shinichi Kaneda (金田 進一). In Super Hero Taisen, his voice is provided by Kimito Totani, who also portrays Daiki Kaito/Kamen Rider Diend.

Black Mars
In the wake of Apollo Geist's defeat, it was originally planned to introduce a new G.O.D. executive named Black Mars (ブラックマルス). However, the unforseen popularity of Apollo Geist changed the course of the series and this character was scrapped.