The Raiwat were once an advanced human civilization. Their technological prowess led them to create the twelve ZODIAC units, immensely powerful living devices with which they sought to create a unified rule over their planet. However, the ZODIAC units suddenly turned berserk and started attacking the Raiwat. In order to stop the ZODIACs, the Yuda Clan create a 13th ZODIAC core, the Ophiucus, but instead of using it they decide to flee their homeworld and take the Ophiucus with them, leaving the remaining Raiwat to fend for themselves against the rampaging ZODIAC units. The Yuda Clan eventually reach Earth, where they established themselves.
After a long struggle, the Raiwat were finally able to deactivate the ZODIAC units, but not only their civilization was destroyed and most of their population annihilated, their homeworld was left a barely-inhabitable wasteland. Forced to adapt to this new environment, the Raiwat ended mutating into half-man, half-beast humanoid creatures. It would take centuries for their homeworld to recover and for the Raiwat to rebuild their civilization. Having nurtured a deep grudge against the traitorous Yuda Clan all this time, they finally decide to get their revenge, sending a massive fleet to Earth and reactivating the ZODIAC units to annihilate the "Descendants of Yuda".
The Raiwat attacks Earth in the middle of the conflict between the Global Unified Army, the oppressive rulers of Earth, and the Valkyness, a resistance force which had sent the ALFI-PH2RX Phoenix 02 in a mission to reach their base on the Moon to deliver a newly-developed optical shield device with the intent of mass-producing it. Known only to the Phoenix's creator, the ship and its optical shield were actually powered by the Ophiucus core. The Global Unified Army is forced into splitting its forces to thwart the Raiwat invasion and intercept the Phoenix before it reaches its goal. Things get a turn for the worse, however, when the Global Unified Army's Saggitarius fleet is destroyed and the Cancer ship is attacked by the ZODIAC Virgo (not to be confused with GUA version of Virgo), causing it to fall into the Moon's surface and explode, destroying the Valkyness base in the process.
Faced with no other choice, the two warring factions put their enmities aside and decide to join forces to repel the Raiwat invasion, but the power of the ZODIACs proves to be too great, as the ZODIAC Virgo alone defeats most of the human's forces and eventually destroys the Phoenix, killing its unnamed pilot. However the destruction of the Phoenix causes the Ophiucus Core to awaken, transforming the wreckage of the ship into the ZODIAC Ophiucus, which immediately begins its mission to destroy all ZODIAC units. Ophiucus destroys Virgo and attacks the other ZODIAC units, causing a catastrophic conflict which would span years and destroy the surface of Earth. In a desperate bid to save themselves from total annihilation, the remaining humans build a new Neural Nest based on ALLTYNEX OS which dispatch the Kamui fighters to fight against the Raiwat and the ZODIAC units. The Kamui fighters manages to hold back the Raiwat, while Ophiucus destroys the ZODIAC units one by one. With only the ZODIAC Libra remaining, the Raiwat dispatch it to fight Ophiucus and immediately retreat their remaining forces, leaving the two ZODIACS and the Kamui fighters fighting behind. With the destruction of Libra, Ophiucus seals its own core and self-destructs, having finally accomplished its mission.
However, unknown to most of Earth's humans but a few high-ranking authorities, Raiwat did not leave because they were facing defeat: they had accomplished what they came for - 1. Take revenge on Yuda Clan for abandoning Raiwat and 2. Get rid of the accursed Zodiac Unit in a war between Earth and Raiwat. With those two successfully completed, Raiwat saw no further point in invading planet Earth and simply left.