KANOHI Mask of Light worn by TOA TAKANUVA.
The Mask of Light was originally forged on the island of ARTAKHA and intended for use by a prophesied Toa of Light. Many thousands of years later, the Brotherhood of Makuta stole the mask from its creators and hit it in one of their fortresses in an effort to prevent this Toa from ever coming to be. Later, after discovering the Brotherhood’s treachery, the TOA HAGAH raided the fortress and stole the mask themselves. Even after being turned into RAHAGA, they were able to successfully spirit the mask away.
The Rahaga hid the mask in the ARCHIVES in METRU NUI. The compartment in which it was concealed could only be opened using six MAKOKI STONES, which the Rahaga hid around the city to keep them from the VISORAK. The TOA HORDIKA retrieved all six stones and found the Avohkii, which gave off a bright glow. Fearing that the glow would attract the attention of the Visorak, Toa Hordika ONEWA used his RHOTUKA SPINNER to conceal the mask in a block of stone.
The TOA METRU later transported that stone to the island of MATA NUI (2) and hid it in a lava cave. Legend stated that the HERALD of the Toa of Light would have to find the mask, it could not be given to him, and so the location of it was kept secret. A MATORAN named TAKUA would eventually stumble upon the Mask of Light while exploring the cavern.
Takua and JALLER were charged by the TURAGA with the duty of finding the Toa of Light. Their adventure took them to many places on the island and exposed them to danger from RAHI and RAHKSHI. Takua later donned the mask and transformed into Takanuva, the Toa of Light. (How the mask was able to trigger such a transformation when normal Great Masks do not has not yet been revealed. It is rumored that the mask may have been infused with Toa power during its creation, and so acted like a TOA STONE.)
The Avohkii can project powerful beams of light energy and banish the darkness. It also brings understanding, turning anger into peace and enemies into allies.
Source: BIONICLE Encyclopedia Updated