The Onu Matoran people are a very strange and solitary race. While outwardly freindly and often very pleasant to be around, they still tend to shy away from most other kinds of Matoran, besides Ko Matoran whom they quite enjoy the company of.
The Onu Matoran are extremely diverse in physiology but manage to have a much more peaceful society than the somewhat similar Le Matoran. Onu Matoran are the oldest type of Matoran besides Av Matoran and have very few inside issues, whether governmental or economic. They are not a warlike people, in spite of their fierce appearances.
Onu Matoran have a variety of physical adaptations that allow them to more easily do what they do best; dig. This fellows right hand has two large obvious talons in place of fingers. While these are probably very affective in battle for slicing up enemies, it is likely they will never see this use and only ever meet dirt and stone.
Many Onu Matoran have large 'shin guards' to protect their legs and lower torsos while drilling. These also provide extra stability during the forementioned activity.
The "Earthdwellers" as they are called by other Matoran have also adopted a widespread physical bioluminescence on various parts of their bodies to help them see deep underground. The actual purpose for Onu Matoran's digging is unknown, and while they always seem to have some excuse for making a new tunnel, most of them sit uninhabited and unutilized. Onu Matoran tunnels often have the negative affect of attracting dangerous rahi since they provide easy access to the rest of the subterranean networks and the huge sewerlike pipes are one of the most dangerous places on Moto Nui, once you get away from civilization.
Toa Ohrdavak has always gotten along seemingly very well with his people, but he always avoids going home unless absolutely necessary for some reason. He often rushes strait there when Onu Koro is in potential danger, which is rare being that it is mostly underground, but avoids opportunities to simply visit.
It has been speculated that this is becuse, while the actual tunnels are very large and can be navigated easily by Toa Ohrdavak, actual Onu Matoran houses are far too small for him to comfortably fit into.