ONI's is mass produced exoskeletons for bodyguard purpose. These unit build based on Furcas. Altough they dont as powerful as Furcas, ONI's can be used up to 8 hours every 24 hours. Because the ONI's itself doesnt have any particular elements, they imbued with 4 different elements based on their color. The blue one often used as disabler because of its capability to froze. Maybe if you collected all of them, in future something good will happen.