They are a group of monsters whose very presence is signaled by a mass amount of mist. Every millennium, the Fog Mother gives birth to a new brood to feed on the occupants of the world she landed on. One such brood was responsible for the mass extinction of the dinosaurs, which were their sole food supply. Seventy five 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.

Machine Beast Mothership Fog Mother
The Fog Mother is an alien parasite in a gold cybernetic battle fortress who sent her three oldest children to obtain the ideal human sacrifice for their "to-be-born" siblings to feed on before devouring the rest of the human race, who had been responsible for exterminating the dinosaurs. Her machine-body can shoot bullets from the gatling guns, shoot a laser from its right eye, emit circular-like sawblades from its left eye, lower its pincers to grab, and emit legs from the torso to attack. She can feel pain if her machine is attacked. After Garai was slain, Fog Mother attempted to digest J, but he was enlarged while killing her newborn spawn. He impaled her with his fist to pull out Kana. J got free from her and broke her pincers and legs before using a Jumbo Rider Kick to heavily damage her body as it starts to self detonate. As a last effort to destroy J, she dragged him back into body, but he got free and killed her with a Rider Punch before escaping as her machine body exploded.

Garai / Cobra Man
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.

Zu / Bee Woman
Assuming the form of a young woman named Zu, her true form is the Bee Woman with 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 attack, 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.

Agito / Lizard Man
Assuming the form of a middle-aged man, his true form is the Lizard Man, 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.
Series:  Kamen Rider J