So far, only two Chaos models have been produced: the 0.8 and the 0.9. Cosmetically these two models are very similar but in reality they are fairly different. The abbreviation Chaos stands for Chrome Hyper Automatic Operation System. Both models appear to be gangly looking, move like a reverse joint and have high jumping abilities.
The first model Chaos 0.8 code named Harrier appears in the mission Prototype MT Test and was developed by Chrome to combat high-performance Murakumo ACs. Chaos 0.8 is gangly looking and is roughly one and a half times the size of an AC. The unit is armed with weapon arms with each arm possessing a pulse rifle that fires a green burst rather than the normal blue or purple blasts and a chain gun. In order to use the chain gun the unit needs to kneel. Its unofficial fan name is Harrier.
The second model Chaos 0.9 code named Hunter is fought in another Prototype MT Test mission. The unit features increased offensive power and is taller than the Chaos 0.8 model possessing roughly twice the size of an AC unit. The unit is armed with weapon arms with each arm possessing a laser rifle and a chain gun. Still like the Chaos 0.8 model in order to use the chain gun the unit needs to kneel. Also new are a missile launcher mounted on the left shoulder and a large antenna that looks like a spoiler on the right shoulder. The AI of the unit has also been improved and the unit is capable of commanding up to 10 of the Harrier units. Its unofficial fan name is Hunter.
The Chaos model appears in a total of three missions as enemies in Armored Core. The first two are testing the prototype models while the second is a large group in the mission Chrome Uprising. They appear in the missions: