Planet Zi is the homeworld of the Zoidian race of humans, along with the massive mechanical beasts they consider partners, The Zoids.
History[]
Long ago, the planet was only home to the techno-organic life forms known as "Zoids" that developed and changed based on data scans of Earth life forms from a super computer at the core of the planet known as the "Zoid Eve". Where the Zoid Eve came from is largely unknown and, therefore, so is the origin of the zoids. A common theory among interplanetary explorers is that the Zoid Eve was a prototype of Cybertron's own "Vector Sigma" super computer.
Origin Century[]
Zoids lived out their lives much the same to any other group of animal species, until Onyx Prime, in reality their creator, decided to perform an experiment. Reaching through time and Space, Onyx Prime gathered a group of humans and genetically altered and adapted them in several ways to form a mutually beneficial relationship with his other creations. In turn, the humans, or "Zoidians" as they're now known as, adapted and changed the Zoids's frames for their own use, allowing them to pilot the massive mechanical animals. Overtime, Onyx Prime saw the benefit in this and reprogrammed the Zoid Eve to catalogue newly created types of zoids, cockpit and all, and have it set up to put them into natural zoid creation as well. At some point, a group of humans who wished to live in harmony with the zoids, wrongly believing the cockpits to be "blasphemous in the eyes of onyx" would go underground and build an underground city near the entrance to the Zoid eve. Perhaps hypocritically so, these people, calling themselves the "original Zoidians" would go on to develop several types of new zoid and technology.
The Chaotic Centuries[]
After several centuries, two groups rose to power, both fueled by zoids on their side, both artificially made and natural born, these two factions would be known as the Helic Republic and Zenebas Empire. The Helic Republic would eventually win the first war, but the Zenebas Empire wouldn't surrender so easily, and thus war continually waged for nearly 200 years. What ultimately put an end to the war would be a meteor shower that wiped out both sides, burying the majority of the zoids and resetting the surviving humans to an early sort of society. There would be a time afterward that the Zenebas Empire aligned with a separate imperial force known as the "Guylos Empire", evidently, the Guylos would be the ones more remembered in history.
Genesis Century[]
In response to the cataclysm, the Zoid Eve shut down, depriving the zoids of the energy it provided them, but it also caused several tree like objects to spring up around the world, known as "Generators", these generators were refined and built into what they'd ultimately be by a group of humans who'd fled into orbit, but they ultimately abandoned them. Various societies of humans sprung up around these Generators and thrived, excavating zoids out of the rubble to work alongside them again. The Generators also seemed to generate some sort of energy that supported the growth of plant and animal life, along with a fuel for zoids known as "Reggel". It's presumed these "Generators" were somehow techno-organic in nature, perhaps the humans in orbit had intended them to be a re-terraforming effort.
Eventually, the people in the orbital station, dubbed "Sora City" ran out of Reggel of their own use and went to a place on world known as "Digu" to get Reggel in exchange for technology, this would result in the formation of the Digald army and their BioZoids. The Digald Army would try to conquer the world and start a new republic, only to be stopped by a boy pilotting an ancient Zoidian Zoid known as the "Murasame Liger".
With peace among the city states, and the people of Sora City once again on world, the people not only rediscovered their history, but also how to turn the zoid eve back on.
Zero Century[]
A hundred years after the end of the Digald War, humanity and zoids have developed the symbiotic and strong relationship they had before, and a new form of sport, Zoid Battles, has sprung up. In these battles, teams of zoids and pilots battle neck 'e neck for the adoration of the public. However illegal groups and people trying to grab for power still existed. A group naming themselves for the historic Guylos Empire would briefly rise to power again, they would conquer many a city state before the Republic, taking up their historic ancestor's name "Helic" in response, would manage to fight them off.
Current Century[]
Things were much like the zero century, but humans now viewed themselves as "Zoidians" due to the connection they shared with their mechanical beast partners. However this relationship wouldn't last long before the Jupiter Empire invaded with a crystal known as "Rare Hertz" which caused the zoids to go out of control. There were few refugees that escaped, but thankfully, Zoids only react to Rare Hertz within the atmosphere of Zi itself, any escapees can breath in peace. Now the Jupiter Empire uses the zoidian and zoid population as slave labor.
Wildlife[]
Many of the plants and animals that are present on Zi other than the Zoids are the descendants of life forms that the humans brought with them when they colonized Zi. These include several species of bovid, canine, and, extremely commonly, fruit trees.