Onu-Matoran were residents of Onu-Koro or Onu-Metru. They commonly had black armor and wore purple or orange masks. On Metru Nui, Onu-Matoran were skilled miners and served as archivists in the Onu-Metru Archives. On Mata Nui, they were also skilled miners. Their favorite sport was Ussal crab racing, and they made up the membership of the Ussalry. Onu-Matoran generally had good night vision but weak eyes in daylight.
The Matoran of Onu-Koro mined the substance known as protodermis for many years as a source of energy without really understanding what it was or where it came from.
Onu-Matoran could see in the dark, and their eyes were sensitive to bright light.
Over time, the Onu-Matoran workers who expanded the Archives underground and the archivists became so accustomed to the dim light underground that the brightness of the twin suns was hard on their eyes.
On Metru Nui, most Onu-Matoran started out as miners, digging for lightstones. They got used to the dark and stale air quickly. If one was lucky, one got the opportunity to become an archivist, though even then one was indoors and underground much of the time.
Of all the residents of Metru Nui, Onu-Matoran were regarded as the most unusual. They spent much of their lives underground, mining lightstones or working deep in the Archives. Citizens from other metru could not understand how they managed to exist like this, but to Onu-Matoran it seemed like the most natural thing in the world. Most Onu-Matoran worked in the Archives, although they did not see it as a job. They loved helping to preserve the history of Metru Nui and would brave any danger to protect the institution. It was very rare that a Vahki had to force an Onu-Matoran to go back to work; given the choice, some would never have left their exhibit halls.
It was popular for Onu-Matoran to sit in on lectures at Ga-Matoran schools.
In Onu-Metru, Onu-Matoran worked as archivists or miners.
On Metru Nui, Onu-Matoran and Ko-Matoran private collectors tended to be the ones most interested in buying rare items from Matoran smugglers.
On Metru Nui, Onu-Matoran's eyes adjusted over time to the point where they could see in the semi-dark. Although much of Onu-Metru was on the surface, Onu-Matoran actually preferred to be in the underground levels of the Archives, because the brightness of the twin suns hurt their sensitive eyes.
To be a maintenance worker was also an occupation in Onu-Metru.
Onu-Matoran on Metru Nui were particularly fond of Ussal crabs.
Onu-Matoran were affiliated with the element of earth. On Metru Nui, they were primarily archivists. On Mata Nui, they were miners.
- The Chief Archivist
- Bomonga (?)
- Toa of Earth merged into Prototype (?)