Warrior Beasts Cleo (along with Keruvinus and Jerunicas), was one of the three most tragic warrior beast in the series. Cleo was a SuperHuman Warrior Beast and the only other Female Cyborg besides Psychoveia, Ralgos, Helena, Marigera and Marquis Janus, while not stronger and imposing as the other warrior Beasts Cleo was far from weak - she had missile launchers in her chest, could fire a glue like substance from the tip of her fingers and could fire laser beams from her eyes, as well release spikes from the top of her head that would block a attack. But her most famous feature was the capability to transform from Warrior Beast into a Human, allowing her to spy on her targets, one of three members to sport such an ability (the others been the Mammalian Warrior Beast Bisone, SuperHuman Warrior Beast Helena and Marquis Janus) - however, her transforming ability was forced, rather than her own will, by remote signal from any of the higher up, like Archduke Gorgon. Prime Minister Argos described her as been a daughter to him.

She was a member of the Empire's Intelligence Army under the Command of Prime Minister Argos and Archduke Gorgon. Cleo was design for infiltration operations and did not enjoy fighting, spending much of her time spying from a far since the reawakening of Mikene, only doing so in self defense. While at first loyal and duty bound to the Empire, her time on the surface made her fond of the Humans, thus developing a desire to become one and went AWOL. While the Empire haunted her down, Cleo moved from place to place using a car, just to be ahead of the Empire. Her only object that she carry in her travel was an ocarina that she played.

Cleo befriended the members of the Science Fortress and the Borot Gang after she saved Shiro from a truck, but was finally caught on by Gorgon, who transformed her into her real form. She was forced to fight Venus A, much to her pain. Bakarasu the Crow ended up knowing the truth, seeing her transformed a second time, and warned the Borot Gang. She contemplated suicide but was stopped by Gorgon. Borot and Venus A catch up to her, but she bury them in an avalanche of boulders and headed to the Science Fortress to destroy it, Tetsuya deployed Great and the two began to fight, but do to the fact she was meant for spying, not fighting, as well her own guilt and lack of will to fight, Great wounded her - Tetsuya tried to fishing her off but was stopped by Boss and Jun who rapidly informed him the Beast was Cleo. Tetsuya tried to give her aid, but Gorgon both seeing a window of opportunity and angered at Cleo's constant defiance, activated her self destruct device, blowing her up and killing her, Great still survived the explosion.

Great carried her body out to sea for an underwater burial (a reminiscent of the Burial of Minerva X, in Mazinger Z). Shiro then played her Ocarina as Tetsuya, Jun and Boss mourned her loss.