Numenos was the Monster of the week on Episode 18 of the Jeeg Anime. It was a robust humanoid Phantom with a Brown and Dark Brown in color, with orange straps in the wrists and waist. It had grey knees, a white face with blue eyes, with a purple spikes and tentacles on the head. Its right arm ended in Sharp blade, which serve as weapon and spew red fire from the mouth. Numenos could also release a Heat shiel around him to repel attack and use its Tentacles to wrapple its enemies for close combat. Numenos could sneek into bases as a Mud/Amoeba form and squeeze into inaccessible areas and was accompany by flying flames. The horns on the head ornament of the torso could also be use as tentacles.

The story starts in a rainy night in Build Base where the staff is in a meeting, discussing new security feature for the Base, specially the Computer Room, from any future Himika attacks: this will lead to the creation of the Flying Capsule Dome. Dairi receive a call mid Meeting of an tanker truck having crashed and exploded in the shore. MechaDon2 arrives to extinguish the fire, just as Hiroshi and Michi arrive; realizing the situation may had been an accident cause by an oil slick, Hiroshi and Michi leave Don to extinguish the fire. Pancho sees fire balls in the woods (Numenos crawling in its Mud form) and Don follows to prevent a fire in the Woods, the Phantom cuts a tree down, MechaDon stumbles onto it and falls, breaking again to pieces.

The following morning, Chibi, Hiroshi and Michi see some of the mud stuck to Hiroshi's bike: when he takes a closer look to it the mud moves, and that's when he realizes there was more to the accident from the night before and take the mud to the Lab for examination. As work progress continues in Build Base, Numenos sneaks in, attacks and kills one of the Staff Members. Later it attempts to kill Michi in the elevator, though she manages to escape and warn the Dairi and the staff. Numenos is then corner by one of the Bulkhead Gates, Michi arrive with the Staff to attack and torn the monster apart: while they think to had succeeded, Numenos reconstitute itself and squeeze to the other side under the Gate, where it transforms into its Phantom Form and attacks the Base from the inside. Hiroshi is warn and runs back to the base but is spotter by Ikima attacking Hiroshi with the Orochi and knock him (as well the MechaDon, which was just passing by) with rock debris. Orochi then flies to Build base to assist Numenos and the Build Base use all of their security and defense measures to repel the attack, though these prove ineffective.

Knowing they are after the Professor Computer, Dairi orders the preparations for the Transfer to the new capsule, while Michi takes off to find Hiroshi: Don and Pancho awaken him in time and the Big Shooter fire the components building up Jeeg and runs back to Build Base while the Shooter fights Orochi. As the staff moves to the Capsule, Dairi stays behind, to watch Numenos break into the Main Computer Room: he activates the transfer and Prof. Shiba's mind is safely downloaded into the Computer Capsule dome, before the Phantom destroys the Old Computer. The Capsule then takes off, with the Phantom now breaking into the Control Room, but is stopped in its tracks from killing Dairi by Jeeg.

Jeeg tries to kill Numenos with Jeeg Breaker, but is repel by a Heat Attack, while Orochi tries to take down the capsule. Numenos burns Jeeg with its fire, then grabs it with its tentacle for a close attack, but Jeeg rips the Blade with Knuckle Bomber and decapitates Numenos with Dynamite Kick, though the monster still moves and unleashes on set of tentacles from the ornament head in the Chest, but Jeeg fires its Spin Storm, destroying Numenos in the process.

Orochi retreats (off screen) as Dairi, Hiroshi, Michi, Don and Pancho celebrate for saving Prof. Shiba, calling the project a success.