The Fog are a group of alien monsters from the 1994 film Kamen Rider J. This parasitic alien race's very presence is signaled by a mass amount of mist and cataclysmic events. Every millennium, the Fog Mother gives birth to a new brood to feed on the life forms of a planet she landed on. One such brood was responsible for the mass extinction of the Earth's dinosaurs, which were their sole food supply. 75 million years later, the Fog Mother returns to Earth with a new brood while her three children perform the ritualistic prayer before going out to obtain the sacrifice for their siblings to feed on so they may consume the human race.
Their attempt failed however, due to the Spirits of Earth choosing Kouji Segawa to become a champion of Earth's lifeforms as Kamen Rider J, who destroyed them and the Fog Mother with his powers.
However, the fate of the previous broods that were successfully born are unknown. This leads to an open-ended possibility that the Fog could return in future installments of the Kamen Rider franchise like with many villains in the series.
Fog Mother is the main antagonist of Kamen Rider J: she is a parasitic alien matriarch residing in a cybernetic fortress who sends her three oldest children, Garai, Zu, and Agito to obtain the ideal human sacrifice for her "to-be-born" offspring (which would make Agito, Zu and Garai their siblings) to feed on before setting out to consume the rest of the humanity.
In the past, she is the one who responsible for extinction of dinosaurs by feeding them to her offspring 70 million years ago. Mother's body is armed with Gatling guns shooting bullets, can shoot an optic laser from her right eye, can launch circular saw blades from her left eye, has pincers to grab located on her lower abdomen, and jut out her legs from the torso for melee attack.
After Garai, Zu and Agito were defeated and slain by Kamen Rider J, Fog Mother takes on J herself and attempts to digest J. But he uses Kamen Rider J Power to grow into a giant while killing all her newborn spawns. J finally impales her with his fist, additionally maiming Mother by breaking her pincers and legs before using a Jumbo Rider Kick to heavily damage her body as it starts to self destruct. As a last-ditch effort to kill J, she attempts to drags him back into her body, but he got free and killed her with a Rider Punch before escaping as her machine body explodes.
The oldest of the Fog Mother's children, assuming the form of a young man called Garai He is called the "Prince" from the Fog Mother. His true form is the Cobra Man who wields a laser saber, a constricting whip, and can use a ball that can turn into a claw. He preceded to carry out the ceremony while his younger siblings battled J. He eventually took on J himself to keep the sacrifice going, until Berry came to his aid in vain. But with Kana now in the egg chamber and Berry knocked out, Garai absorbed the surrounding mist to assume his true form. Garai was even stronger in this form when Kamen Rider J impaled a sharp object in him. Garai used his ball attack on him. When J got free from it, he used the Rider Kick to knock Garai unto the alter, fatally wounding him.
Assuming the form of a young woman named Zu (ズー, Zū), her true form is the Bee Woman (ハチ女, Hachi Onna), armed with the ability to fly with the wings on her head and shoot needles from her hands. She was the one who kidnapped Kana for the sacrifice. Upon news of Agito's death, Zu was sent to avenge her brother. She used her crimson ribbons to trap Kouji and drop him from the skies after shedding her human form. But he assumed Rider form and overpowered her on his bike and on foot.
She shot Kamen Rider J in the arm with one of her needle attacks, grabbing him and taking him into the air. She was mortally wounded upon collision with the Fog Mother's ship, seeing Garai one final time before she died and faded into the mist.
Assuming the form of a middle-aged man, the true form of Agito (アギト?) is the Lizard Man (トカゲ男 Tokage Otoko?), an alligator monster.
He was the one who killed Kouji, bend on killing him again upon learning that Koji was still alive. When encountered the second time by Kouji, he shedded his human form and attacked Kouja and being the first one to encounter Kouji in his Kamen Rider J form.
He overpowered J until he took poked his eye out. Agito attempted to escape by climbing a cliff, but Kamen Rider J killed him by performing a single Rider Punch on his head and Agito fell off the cliff, plummeting to his death.