Omnix

Omnix was an Av-Matoran (disguised as a Ko-Matoran) existing in the Omnix alternate universe who, forging theMask of Reality, shaped reality to his will and became all-powerful before being stopped by the combined power of the Makuta and the Toa.

History
Omnix was an Av-Matoran who originated from Karda Nui, where he was little else but a worker. During the Time Slip, he was transported to Metru Nui and disguised as a Ko-Matoran. However, by accident, he did not lose his memories of Karda Nui and his true Av-Matoran nature. He still posed as a Ko-Matoran, though.

After many years as a lonely scribe in a Knowledge Tower, Omnix took a trip to the Onu-Metru Archives to try to find a certain manuscript. In his hurry to find it, he became lost, and stumbled upon a secret chamber, containing the Great Beings' original designs for the Mask of Reality. Taking the schematics, and disguising himself as a Ta-Matoran, he snuck into a Ta-Metru forge and created the mask using a discarded prototype of a different mask. Using it, Omnix transformed himself into a powerful new form, acquired many legendary Kanohi, the Avohkii, Guhjii, Ignika, and Vahi, as well as a golden Hau, and created two weapons through which he could channel the masks' powers. Using the powers of all his masks, he conquered and opressed the citizens of Metru Nui. Even Teridax himself could not defeat him, so the Brotherhood of Makuta was forced to ally itself with Lhikan and his Toa team in order to defeat Omnix, their common enemy. They finally defeated him by taking him by surprise, allowing them to remove the Mask of Reality. Lhikan used it to return everything to normal and wipe Omnix's and the Matorans' memories of the mask, and Teridax then crushed the mask underfoot. As a product of the Makuta/Toa alliance, Teridax never unleashed the virus that would incapacitate Mata Nui, and the Brotherhood never turned against the Matoran. Thus the Matoran universe lived on in peace.

Powers
As an Av-Matoran, Omnix had innate Light abilities, and the ability to change his color scheme at will.

While weilding the Mask of Reality, Omnix had the ability to change reality to his liking. Using his additional masks, which he acquired by using the Mask of Reality, he possessed Toa-level Light powers; the abilities to speed up and slow down time, create a force field to block expected attacks, and warp the space around him; and the powers of the Ignika, the extent of which is unknown.