Kaio is an Ultimate Form Spectrobe and is considered by some a guardian or god of the Kaio system. It is unknown if Kaio has been summoned at all prior to Rallen but engravings in the Green Ruins in the Tree of Life depict Kaio facing a creature, likely a Krawl.
At one point, Kaio was placed in the form of a fossil that was divided into five shards, which were scattered across the several planets of the Kaio system. Kaio is dragon-like in appearance. It has two arms, six wings, and a tail, but no legs. Its body shines in a light blue color.