During the Golden Age, Astraea created 88 constellations by rearranging the billions of stars in her image, and the 12 Astral Courts for 12 of them to rule. However, she wanted the strongest 12 of them to sit on the thrones in the courts. So she organized a ritualistic fight to determine the 12 strongest constellations. The fight would take place in an alternate reality, disengaged from time, after the 12th court had finished his/her reign (Earth's 19th January) to determine inheriting constellations of the throne. But for Khaos – the singularity and the allfather of the Greek deities – he took the fight as his entertainment.

One day, Khaos decided that brawling with the power of elements aren't enough to satiate him. So he gave the 88 constellations an infinite supply of the 118 elements – from hydrogen to ununoctium – to create their own Gundams to compete in the ritualistic fight. With the Gundams, the fights became more and more interesting for Khaos. And the winners from when the 88 constellations have the Gundams stayed the same. Those constellations, are the Zodiacs we know of today.

In the year 2354, spiritual communication is a common feature in the communication devices of the time. The Zodiacs took this opportunity to find humans of their respective star signs to be their heirs of the thrones, and to reintroduce them to the new competitive sport of the Gundam Fight. However, the other 76 constellations and Khaos were disgusted by this act, especially coming from the Zodiacs. So facing the upcoming threat, 11 of the Zodiacs entrusted the Gundams to the humans – for their ascension into a demigod if they successfully defended the courts from the threat – while the Zodiac constellations defended the court itself. The motive of attack from the 76 Zodiacs is simple : Lowly humans who destroyed the world created by Gods must not be interacted with.

In 2355, only 20 Gundams are known to be operable. That is when the real battle begins.