Aquatic Warrior Beast Giraginga and Multi-Capable Warrior Beast Isacron were the Warrior Beast duo only featured on Episode 29 of the Great Mazinger series.

Giraginga resembles the popular images of characters from the Cthulhu Mythos including the cephalopod-like head that features four tentacles dangling from the lower jaw, a blue upper head, green fins on the side of the head, a black face, heterochromic eyes with a pink left eye and yellow right eye. The body resembles that of a shrimp with a tail for a lower body, missile launchers on the torso, and a pair of spiked pincers for forelimbs. On the back are a pair of indigo wings that allow Giraginga flight. Giraginga is capable of swimming using its tail to control movement underwater and can fly through its wings. The torso fires missiles from the four tubes on its body, while the head can act as a rocket – this interesting as this were the suppose true face is located and losing it did not cause the lose of control functions of the Monster. The tentacles on its face can also be used to restrain and lash at opponents. Giraginga is one a few Warrior Beasts to not contained the brain were the suppose true face is located – an orange colored face, with a pair of bull-like horns - the Brain seems to be located in the actual head of the Monster (based on actions taking by the Beast the lead to its downfall).

Isacron was a large Warrior Beast of the intelligence Army, despite its Humanoid look, he was identified as a Multi-Capable Warrior Beast. He had a gray mouth covering and yellow slit eyes, a large single horn central on his head and two large red horns either side of his head. He had a red chest plate and large spiked shoulders, one hand had a large spike in place of an actual hand. His true face was located on the belly with blue skin and green hair. Isacron could conduct and use electricity as a weapon, he could fly and fire missiles from his shoulders and left hand.

The two are commission into action under the Supervision of Prime Minister Argos, by order of the Emperor himself, much to the determinant of the Great General of Darkness after his many failings to deal with the Fortress and the Great Mazinger Team. Marquis Janus provided the Command of the Operation. The Operation called to use The Volcanic Base Gorgon to be in close proximity to the Fortress, but are detected by the Fortress which begins to attack with Torpedoes, Janus response by sending Dolphins trained to kamikaze onto the Torpedoes - DA WHORE! ):<

As Tetsuya launches Great to counter attack against the Volcanic base he is detected by Aquatic General Angoras on the Mikelos, who is providing assistance in the operation by launching Giraginga and the two proceed to fight – as Great is distracted, Janus emerges and covers the region with an anti radar fog, blocking its signal from the fortress' radar. As Great cuts the wings of Giraginga, the beast in return blast Great out of the sky with its Missile helmet and falls, moving the fight underwater. Not far, the Volcanic base reaches land and launches Isacron, who encounters by chance Boss Borot, who ran off before he was shutdown by Isacron's electric attack – this blast of energy is detected by the lab, which launches Venus A to investigate. Meanwhile, Giraginga continues to bash Great all over the sea floor, Tetsuya regains its control and attempts to kill Giraginga with the Great Sword but it avoids it and hunts Great Mazinger. Great releases his great booster to stop, turns his swords backwards and Giraginga impales itself with it through one of the eyes. This destroys the brain and the monster convulses all around in agony, Great finishes the Beast by slicing it half, then departed towards the lab to help clear the fog.

Back with Isacron, it confronted Borot once more, and nailed him onto a Mountain side, Venus arrived to provide assistance and avoided its attacks, while Borot releases itself and crashes onto a crate which contained he opens and finds a Camera inside (Don't ask, that IS in the episode, Borot finds a Borot size crate with a Borot size Camera in it – Size back then in 70s Anime was just … a “convenience” with Borot around). Borot then uses it to blind the beast with the flashes to help out Jun, of course the Beast gets wise, breaks the camera, punches Borot, tossing him over Venus and the proceeds to attempt to destroy them when Great arrives and fights Isacron for a few seconds before cutting the Beast through the waist (where the true face is located), however, the upper body crashes onto Great Mazinger and explodes, knocking Tetsuya out.

Mikelos then launches to attack the Science Fortress, which attempts to submerge, but is stop by the warship, crashing onto it and pushing it to the shore line. With the Mechas out of commission and the lab about to be crushed, Prof. Kabuto is force to activate the “AZ plan” – which extends Great Mazinger's Launching Pod out and revealing to be a Photon Laser Cannon. It opens fire and hits Mikelos which causes it to crash into the sea, realizing its power, Marquis Janus orders the retreat (and for as far as I am aware, AZ Plan is NEVER brought about, ever AGAIN!!!).