Originally this organization-or a similar one with several of the same members-existed under the name Hand of Artakha, and preceded the Toa as the defenders of the universe inhabited by the Matoran and other beings. When the Toa came into being, several members of the Hand of Artakha formed the Order of Mata Nui to serve as a secret society who would guard the universe unseen and through means that the more heroic Toa couldn't employ. They would thus act in secrecy for tens of thousands of years, checking the actions of the villainous Brotherhood of Makuta and the Dark Hunters while maintaining their status in hiding. Among the actions taken by them was placing guards over the Ignika, the Kanohi Mask of Life; maintaining a prison to which the worst criminals in the universe were forever condemned; and planting evidence on Metru Nui indicating that the Matoran who became the Toa Metru had been wrongly selected, though this was in fact a ploy to trick Teridax.
Eventually the Order of Mata Nui came out of hiding in order to engage the Brotherhood in open war, and demonstrated their moral ambiguity further by allying with the Dark Hunters and other villains in order to address the threat of the Makuta. They struck a series of blows against the Brotherhood, but failed to stop Teridax from seizing control of the universe. He then destroyed their home base, resulting in the deaths of most of the Order members; the remainder joined in resisting Teridax's occupation before emigrating to Spherus Magna following Teridax's demise.
The first Toa ever created, a Toa of Water who led the Hand of Artakha before forming the Order of Mata Nui; due to the nature of the Order she chose to hold herself above the Toa code, which among other things prohibited Toa from killing their enemies except under extreme circumstances. She wielded a mace and shield and wore the Mask of Psychometry, which gave her the power to determine where an object had come from. She led the Order for millennia and later commanded their entrance into open war, only to end up trapped inside the brain of the Great Spirit robot after Teridax took it over. Eventually she and several other inhabitants of the robot were ejected into space and then brought to Bota Magna by Vezon, where they met one of the Great Beings.
An axe-wielding warrior who was part of the Hand of Artakha; after that group was dissolved Axonn briefly went on a spree of conquest before being recruited to the Order. He was eventually assigned to Voya Nui as one of the protectors of the Mask of Life.
A monstrous member of the Order whose primary task was taking dangerous criminals to the Pit, a maximum security prison, after they had been defeated in battle. He was later killed by Makuta Icarax, but was one of several characters revealed to have been revived aboard the Red Star.
A sword-wielding former scholar and former servant of the Brotherhood; he befriended Axonn and the pair were assigned to Voya Nui together, but over time Brutaka came to believe that Mata Nui had forsaken them.
A weapons master who served in the Hand of Artakha before joining the Order; he was responsible both for recruiting his old comrade Axonn and for training the Toa Mata after they were created. He was subsequently assigned to the Pit as its jailer, but was killed during a mass breakout resulting from Mata Nui falling into a coma. The Kanohi Ignika later transformed Dekar into a duplicate of Hydraxon with many of the original's memories.
A Ko-Matoran who joined the Order so as to put a stop to his Makuta-aligned nemesis, Vultraz.
A tall warrior and one of Helryx's most trusted aids.
"Ancient": A Dark Hunter who was recruited to the Order of Mata Nui, serving as their informant and later making the Dark Hunters aware of the Order's existence. He was later killed by the Shadowed One to prevent him from revealing the secret of a number of vials that that the Shadowed One found.
Jerbraz: A warrior who was rendered invisible as a result of the Order's experiments and carries a sword that was similarly affected; later recruited the Matoran Mazeka into the organization.
Johmak: A black-armored female warrior who wore a helmet and carried a shield; she could dissolve into a cloud of black crystals and fly through the air before reforming.
Krakua: A Toa of Sonics originally enlisted to serve as an envoy between the Order and other beings, later brought on as a full member. He wears the Kanohi Suletu of Telepathy and wields a Sonic Sword.
Tobduk: A tall warrior who became a being of pure rage after his homeland was ravaged by the Visorak. He became the Order's go-to assassin, notably eliminating all beings known to have knowledge of the whereabouts of the island of Artakha.
- A member of Botar's species who took his place after he was killed by Icarax.
- A four-armed member who was killed by Voporak.
- A winged female member who aided Tahu in tracking Makuta's Rahkshi army on its way to invade Bara Magna.