When the Toa had gathered all of the Great Masks of Power, they were each rewarded with a Gold Mask. Each Gold Mask had the power of all six types of Great Mask which they had collected: Hau, Kakama, Pakari, Miru, Akaku, and Kaukau.
The gold masks were easily the most powerful Kanohi, containing the energies of Kanohi Hau, Kakama, Pakari, Miru, Akaku, and Kaukau. A Toa wearing a gold mask could access all of the powers of the Kanohi masks at will.
Each Toa gathered six Kanohi Masks of Power and used them to obtain a Golden Kanohi. Each golden mask contained all the powers of the other six masks combined.
Onua staggered as waves of power blasted through him when putting on his golden Kanohi for the first time. The golden mask united all the powers of the other six, except it was even stronger.
Gold Kanohi were made from protodermis, not actual gold.