Hercules is a character from the television series Kamen Rider X, where he appears as an antagonist. He is a mythological monster-type cyborg, also referred to as a Mythological Kaijin, created by the secret organization known as the GOD机关. His design and name are derived from the legendary hero Hercules from Greek mythology, known for his immense strength.

In terms of background, Hercules was manufactured by the GOD organization to serve as one of their operatives. His primary mission is to sabotage Japans oil imports by targeting a special envoy from the Kingdom of Adabu who is traveling to Japan. His objectives are to either assassinate or kidnap this envoy, thereby dealing a severe blow to the Japanese economy.

Hercules is a formidable combatant, living up to his namesake as the "strong man Hercules". His notable abilities include superhuman strength, which allows him to easily lift and throw large rocks and automobiles. He is heavily armed for close-quarters battle, wielding a club as his main weapon and carrying a sword on his left hip. For defense, he employs a shield emblazoned with the GOD organization's symbol. Beyond his physical prowess, he possesses more unconventional abilities, such as the power to control poisonous spiders and the ability to render himself transparent.

The character is also depicted as cunning and perceptive. When Kamen Rider X, the hero whose real name is Keisuke Jin, disguises himself as the envoy, Hercules quickly sees through the ruse. He then orders separate GOD combat operatives to capture the real envoy, demonstrating that he relies on strategy in addition to raw power. Physically, his appearance is distinctive and monstrous. His face consists of two interconnected visages, one human and one beast-like, and he has long, flowing red hair. His body is primarily colored with a striking red and blue pattern. His helmet features a likeness of the Nemean Lion, which in mythology was the first creature the hero Hercules defeated and whose hide he later wore.

In his role within the story, Hercules is the primary enemy encountered by the protagonist in his third mission. He is a direct subordinate of the GOD organization. The final confrontation with Kamen Rider X is a tough battle, as Hercules is a resilient opponent with no clear weaknesses in either offense or defense, thanks to his shield. However, he is ultimately defeated when he receives the X Kick, the riders signature finishing move. He withstands the first kick and manages to use the momentum to quickly circle behind his foe, but his follow-up attack is evaded. A second X Kick then mortally wounds him. Despite his grievous injuries, he musters his last bit of strength to swing his sword at Kamen Rider X, but the attack misses, and he explodes.

Regarding his development and key relationships, Hercules maintains a direct association with the GOD organization, acting as one of its primary agents in the field. His sole opposition is Kamen Rider X, who thwarts his mission. Although he is destroyed in his initial appearance, he reappears later in the series. In episode twenty-one, he is revived as a member of a monster squadron that once again challenges Kamen Rider X, only to be defeated once more. He also makes a further reappearance as a revived version in the theatrical film Five Riders vs. King Dark.