Onu-Matoran were cave-dwelling Matoran with miniscule control over the element of Earth.
As Matoran of Earth, they spent most of their lives underground. As a result of this, their eyes had adapted to function in little light. This meant that they were easily blinded by bright lights. Onu-Matoran were also known for their strength and durability. Onu-Matoran also tended to put their faith in the past and what could be learned from it. The main Onu-Matoran virtues were Unity, Duty and Destiny, and the principle they get from the virtues is Prosperity. In Metru Nui, most Onu-Matoran worked in the Archives or as Miners. They usually started out as miners before moving their way up to working in the Archives. On Mata Nui, Protodermis and lightstone mining were their main occupations. They operated the Ussalry — a defense force that rode Ussals as their steeds. Onu-Matoran had green eyes and wore mainly black armor, often with additional shades of purple, tan and even orange. All Onu-Matoran were male.