Mata Nui (Being)

Mata Nui is the Great Spirit sent down from Artakha by the Great Beings to care for the Matoran. He made sure everything was in order, such as the laws of physics, gravity, and all kinds of other stuff.

However, Makuta, his brother, followed him down from Artakha and caused shadow and dispair for the Matoran, founding the Brotherhood of Makuta and various other organizations. He then made Mata Nui sick and put a sort of sleep spell on him, causing Mata Nui to sleep.

After Makuta was defeated by Takanuva, the Matoran returned to Metru Nui. They thought that Mata Nui had been awakened, but were wrong. Dume revealed to them that Mata Nui was dying - and the only thing that can save him is the Mask of Life.