Dorumos was a SuperHuman Type Warrior Beast and the the featured Monster of the week on Ep.38 of the Great Mazinger, this Episode also marks the first time the Great Marshall introduces itself to the protagonists after his initial series introduction. Dorumos had Dark Blue oval shape head adorn with sharp horn blade, these serve as Boomerangs to cut anything. His Red Upper torso had two rocket launchers on it shoulders on each side of the head, with arms were Grey with Green color wristbands, with two blades fins coming out from the sides, and his legs were Grey with red and Dark Green bands. His real face was located in the chest.

The Great Marshall orders Julicaesar to take the Beast and the Mikelos in a plan to steal Great Mazinger and on its way, Dorumos is launched. He first fought Borot, Venus A and Junior while the three were training, keeping them at bay while Mikene went forth with the main part of the plan, attacking the Fortress. As Great was launched, Mikelos distracts Tetsuya from docking and launch Robot Rockets that docked with and took Great onto the Mikelos. Tetsuya tried to stopped them, but his effort were blocked by Dorumos, who came to assist in the fire fight between Mikelos and the Fortress and cut the fin of the condor, causing it to crash. In the standoff, Mikelos suffered some level of damage that forced it to land in the Volcano Base for repairs.

As the group pounders their situation, the Great Marshall introduces himself, promising to use Great as means to destroy the Fortress. An impatient Julicaesar berates Janus for the slow speed of the repairs. After repairs on the Brain Condor, Mechas and lab are done, they set off in search of the Volcano Base, as they are detected, Dorumos is launched and goes after Venus first, while Testuya attempted to divert its attention, Borot is launched from Greats Launcher Tube and grabs onto the beast's legs, kicking him in the abdomen various time, before Dorumos cut its arms off. The Volcano Base emerges and joins, but Tetsuya proceeded to blast the base with the Science Fortress joining causing great damage, while Dorumos fought Venus A.

At that moment, The Marshall orders Julicaesar to use the commotion to escape on the now repair Mikelos, but as soon it takes off, it comes under attack – weaponry of both the Condor and the Fortress been enough that rips a hole in the bottom of the ship, causing Great to slip through. Tetsuya immediately docks with Great and in time as Dorumos was finished with Venus. Great Mazinger takes Dorumos out in a combo of Thunder Break, disorienting him, then Navel Missile and Great Boomerang which ripped its arms off, and finally Breast Burn blowing him up. With Great Mazinger back, the Damage Mikelos and Volcano base retreated, and an angry Great Marshall passing blame for the commanders failures, and having met their newest enemy, the heroes vow to face any plan he has up in the works.