Mumbei, known in the English version as Moonbay, is a free-spirited transporter who operates on the planet Zi. She pilots a custom-painted Gustav, a large armored insect-type Zoid capable of hauling heavy cargo. She first crosses paths with Van Flyheight and Fiona when the Shield Liger breaks down in the desert, and after sacrificing her own cargo of explosives to save them from a swarm of Sleeper Zoids, she demands that they work to pay off her lost earnings, thus joining the group. Moonbay comes from an extraordinarily large family of thirty-three children, a background that taught her how to be social and resourceful from a young age. She inherited from her parents an innate ability to sense the flow of energy within Zoids, making her an exceptional mechanic who can identify weak points and pressure points on a machine just by feel. She also knows moxibustion techniques, applying pressure to a Zoid’s energy points to accelerate its recovery. In personality, Moonbay is outspoken, practical, and independent. She is motivated primarily by money and will take jobs from the Helic Republic, the Guylos Empire, or anyone else who pays well. Despite this mercenary streak, she possesses a kind and honorable nature and is quick to defend herself and her friends when threatened. She is also an excellent cook and knows how to manage finances carefully. Her role in the story is that of a logistical support and mechanic for the main group, providing transportation, repairs, and local knowledge throughout their journey. She shares a long-standing, bickering relationship with the mercenary Irvine, whom she knew before the series began, and while she refuses to admit it, she clearly harbors feelings for him. Over the course of both Chaotic Century and the follow-up Guardian Force, Moonbay remains a reliable and resourceful companion, using her mechanical talents and streetwise savvy to keep the team moving. She does not engage in direct combat herself but is always ready to help out when trouble arises. Her development is subtle; she starts as a purely transactional character but gradually shows deeper loyalty to her friends, though she never loses her enterprising nature. Her notable abilities include advanced Zoid repair and tuning, piloting the Gustav for long-distance hauling and as a mobile base, and her inherited energy-sensing gift, which makes her invaluable for keeping Zoids in peak condition.