Khaos (also known as Cha Os) is the main antagonist in most of the Thunder Force series. A massive supercomputer and artificial intelligence, Khaos has the ability to control and command the forces of the ORN Empire. The computer is described as being very hostile and omnicidal, and a primary threat to the Galaxy Federation.
Khaos is a huge bio-computer created by humans in the beginning of the space age. Capable of storing data at impressive speeds, it eventually became self-conscious and acquired a free will of its own. Deeming humanity as inferior beings, it decided to exterminate human life from the universe (apparently, its human creators gave it that idea), and for this end, Khaos gathered military power and created the ORN Empire. Its main opposition comes from the Galaxy Federation and their Fire LEO series of starfighters. Khaos was destroyed once in the events of Thunder Force III, but it survived and appeared again in Thunder Force IV, only to be destroyed once more. Despite its destruction, it managed to upload its data onto the Fire LEO-04 "Rynex". The ensuing explosion made Rynex drift in space aimlessly (their pilots had ejected at the last second) until it reached the Solar System (and subsequently, Earth), which led to the events of Thunder Force V.
Even without their leader, the ORN Empire continued to exist under the rule of ORN Faust and was never truly defeated. It demonstrated this ability by installing itself on the abandoned Rynex and taking over Babel, the Guardian, and all the Earth-made Vasteel Technology weaponry to launch massive attacks against the human race in order to destroy and rebuild Earth with Vasteel technology and create a new ORN Empire. While Khaos, using the interior of the Guardian on Judgement Sword, created a female body shaped chrysalis known as Guardian Animus, Khaos used it to evolve into a stronger being known as Khaos Ascendant. In a final attempt to take over the Earth, Khaos Ascendant tried to escape from the dataspace of Judgement Sword, only to be defeated by a lone RVR-02 "Vambrace" piloted by Cenes Crawford.
With Khaos absent, the ORN Empire created the ORN Emperor, their new leader, as well as the final boss in Thunder Force VI. Unlike Khaos, the ORN Emperor was created as an organic entity and it was on its embryonary phase. Despite the massive amount of power its new body demonstrated, it was defeated by the combined teamwork of Earth and the Galaxy Federation.
- Khaos was the only enemy that was unidentified by REFFI, as the program only identified it as "Unknown".
- The female body chrysalis growing belly is a reference to the stages of pregnancy, implying that Khaos is using the energy of the RVR-02's weapons to grow and increase its own strength before hatching.
- Khaos Ascendant seems to be stronger than the Guardian itself, at the point of crashing REFFI during the enemy data scan prior to the battle.
- Of all the digital entities inside Judgement Sword, Khaos is the only one who physically explodes rather than being "deleted".
- Khaos' plan of destroying and rebuilding Earth with Vasteel Technology shares similarities with Con-Human from RayForce (GunLock), who succeeded on rebuliding the planet as his body and installing itself as the new core, but failed in destroying humanity, which lead to its demise.