The Raiwat Zodiacs (or ZODIACS) are revealed to be the true enemy in RefleX, first introduced when a ZODIAC (assumed to be Virgo) destroys a damaged Cancer (Human) with its power laser cannons. The only ones seen and fought in RefleX are Virgo (Raiwat) and Libra (Raiwat). The other ten are destoyed in the time between the last two levels of Reflex.
The ZODIACS were a series of 12 (+1 unfinished) automated weapon platforms created by the Raiwat for unknown reasons initially. ZODIACS themselves are made of two important parts - a Frame, the physical ship which is itself a capable weapons platfrom, and a Core, which gives its Frame enormous new power and, upon activation, noticable energy wings. Apparently, some time after their activation the ZODIACS went berserk and turned against their creators, resulting in most of their civilization being decimated. To counter this, a final ZODIAC was intended to be built to destroy the other ZODIACS and then shut down after the objective was complete. For unknown reasons this ZODIAC, called Ophiuchus, was on the verge of completion, with both the Ophiuchus Core and Frame complete but separate, when the other Zodiacs were shut down by having their cores sealed.
After an undisclosed amount of time, the Raiwats decided to wage war on Earth and released the ZODIACS upon Earth's forces. Before this, Dr. Denys somehow got the Ophiuchus core and after extensive studies of it designed and created the Human Zodiacs to counter the Raiwat ZODIACS and also used the core itself to create the Phoenix Mk. 2 to, ironically, assist in the rebellion against the Earth world government.
After Ophiuchus destroys the other twelve Zodiacs in Reflex it activates a seal on its own core to prevent it from being used to continue the destruction caused by Zodiacs. However, humanity recovers the Ophiuchus core and uses it to power a new weapon. This marks the last appearance of the Zodiac cores, as this new weapon, designated Kamui Zero, is destroyed by the player ship in Kamui.
The original Frame which would have housed the Ophuichus Core appears on its own as the final guardian before fighting Alltynex during ALLTYNEX Second. It is significantly weaker in comparison to the other Zodiacs because it does not have the core installed, and thus cannot use its shield or the full extent of its weapons.