Kairus is an intensely hateful being, a corrupt, violent entity desiring only the furthering of its master's goal; the eternal, all-encompassing destruction of life. Born of alien, organic matter and unlike almost all of the other beings in the Toa's world, its insane hatred only grew more insurmountable.
Kairus was "born" as a hideous massive, organic being created in the Tower, to serve the Wrathbringer's forces.
Some time after its creation, it left the Tower, kidnapping a wounded Sylah and severing her mind from her body, placing her mind inside a mysterious dimension. Kairus then coerced Shadus into attacking 'Kea, and stole both away to the Tower.
Forcing Rahzahkea into a prison cell with Cloak, disguised as Elkara, Kairus vanished after leading Shadus to the imprisoned Sylah, trying to make him choose between saving her soul or body. However, Shadus rebelled and saved both, dueling the organic abomination briefly before being cornered by it in the Tower's throne room.
Kairus briefly assumed its Corruptus form, stopping one of Shadus' attacks with a bolt of pure Wrath energy., before being talked down by Selarial, who banished it momentarily.