Zivon

"If there is a way to stop a Zivon, I don't know it. It can be thrown the length of a metru, have a building dropped on it, be slammed head first in to the ground, and come right back at you again. Smoke and flame can sometimes slow it down, but not defeat it. At best, you can hope it will be trapped in the Zone of Darkness again if a Kahgarak chooses to send it there. Otherwise, the appearance of a Zivon is a good sign that it is time to move elsewhere."

- Rahaga Norik

The Zivon was a large Rahi created by the Brotherhood of Makuta that lived in the Zone of Darkness and could only be summoned by the Kahgarak's Rhotuka Spinner. It was roughly 40 feet tall and had more than once, devoured most of the Visorak Horde as a victory celebration, because the Zivon only fought to protect its prey, the Visorak. It's spinners caused blindness, deafness, muteness, and numbness. The Zivon's stinger was probably the only object that could penetrate a Tahtorak's armor. This Rahi also had the ability to shoot webbing from its legs to entangle a foe.

The only known specimen of Zivon was summoned to the ruined city of Metru Nui by Sidorak shortly after the Great Cataclysm. This was done in an attempt to destroy the Toa Hordika once and for all. It was thwarted by the appearance of a Tahtorak and the shapeshifting Rahi named Krahka. During the climax of the battle, a Kahgarak sent a Rhotuka spinner at Tahtorak, but Krahka rammed herself into the Zivon, forcing all three of them to be in physical contact when the spinner struck. As a result, all three were sucked into the Zone of Shadow. A thousand years later, Krahka and Tahtorak escaped when Brutaka failed in his attempt to send Axonn into the Field. Zivon is now effectively trapped, for all known ways of summoning it are gone; Vezon, wearing the Brotherhood's Olmak was in the way of a wave of energized protodermis, Brutaka's Olmak has been shattered by Teridax, and all of the Visorak are now dead, thanks to the Toa Mahri and the Order of Mata Nui.