Grecios

 Grecios is a Superhuman Warrior Beast that appeared in episode 7 of Great Mazinger as the monster-of-the-week.

Appearance
Grecios has a similar appearance to Mazinger Z but instead of a Pilder on the crown area, its true face is located there, which resembles an old man with grey hair. On its torso is a cage used for holding prisoners. The most extended parts of its body including the shoulders, forearms, and crown area are blue. It has a red chest; a purple neck, lower jaw, and torso. On its waist is a yellow belt with red bolts and a black buckle. The most logical explanation for Grecios' similarity to Mazinger is because Shinichi saw him defend Japan from Dr. Hell.

Abilities and Equipment
Grecios is capable of flight and burrowing underground. Its left hand is a pincer that it uses for combat and burrowing. The cell on its abdomen can capture human sized targets and heats up to torture them. For ranged weaponry, Grecios uses heat beams shot from its eyes and its forehead shoots a paralyzing beam.

History
Shiro's class are drawing while one boy called Shinichi says he has a giant robot in his house. He draws a robot very similar to Mazinger Z, wich causes Shiro to call him a liar. Shinichi bets that he'll show it the next day in a park.

Shinichi's drawing is photographed by Duke Gorgon, who in turn sends it to the Great General of Darkness. It is not clear but it appears that they buit a Warrior Beast similar to the drawing - Grecios.

The next day Shinichi takes the class to the park. Grecios tunnels underneath the park and appears, revealing himself as a Warrior Beast. He captures Shinichi and puts him in the cage cell in its abdomen.

Grecios heads for the Science Lab, where is faced by Venus A and Boss Borot, quickly defeating them. Jun realizes she can't destroy the Warrior Beast without harming the kid. General Julicaesar speaks through Grecios, demanding Dr. Kabuto to surrender the Science Lab or he will kill the boy, heating up the cell in the abdomen. Tetsuya finally comes to the Science Lab and launch the Great Mazinger. Grecios uses its paralyzing beam on the Great. Seeing there's no way to fight Grecios without harming Shinichi, Tetsuya comes out with a strategy. Venus A uses her Breast Missiles to blow up one of Grecios' legs, inmobilizing him. Tetsuya gets out of Great Mazinger and climbs onto Grecios' head stabbing him in his real face's eyes, blinding him. Finally, Tetsuya gets onto the Great and cuts Grecios in half with the Mazinger Sword, releasing the cell. With the kid safe, Tetsuya finishes the Warrior Beast with a Thunder Break.

Trivia

 * Grecios is similar to Mazinger Z because Shiro's classmate saw the mecha destroy Dr. Hell's Mechanical Beasts.