Kaxia was a armor inside a bat-like rahi called Kaxbat. Mata Nui created it to aid the Makuta back then. But Kaxbat had something else inside his mind than helping. A mysterious matoran found Kaxbat and they for,ed a partnership. Together, they became Kaxia and ran amok killing motarans, destroying cities until Mata Nui had enough. But even the great Spirit can't even defeat the Evil Killing Machine. Just then Makuta came wih an orb, sealing Kaxia. 100 years later, another user stole the power and contiuned the legacy. Then another and another. When the 4th Kaxia was sealed it remaine dthere for more than 100,000,000 years until a matoran named Kaga finds Kaxbat-the-5th. Together they plan, not to follow the Kaxia legacy, but to kill Makuta in Mata Nui's body, and save the world.
Mask and Abilities
As Kaxia, the user has unlimited power and using telekinesis. There is so much power that all can't be named. The user can transform into Kaxia and revert into their previous form whenever they want.
But when Kaga became Kaxia, most powers were sealed because Kaxia is only for evil and plus the power could take over Kaga. In order not to prevent this, Kaxbat uses some power of the sealing orb to stop Kaxia from completely taking over Kaga. but they can still transform and revert.