Kojol

Kojol was a Makuta, and was assigned to the Artakha area. He was highly secretive, never revealing his knowledge to even his fellow Makuta, not even the location of Artakha. 1,500 years before the Great Cataclysm, he led a strike force of Rahkshi and Visorak into Artakha and stole the Kanohi Mask of Light, so that the Brotherhood of Makuta could ensure no Toa of Light ever came to be. Kojol was killed when, in response to the Brotherhood's attack, the Ruler of Artakha asked the Order of Mata Nui to destroy all maps with Artakha on them and kill anyone who knew its location. The Order of Mata Nui tampered with his metal-eating virus so that the virus would destroy Protosteel and his essence was incinerated in a furnace at Xia. How exactly his essence ended up in the furnace is unknown.

Dark Mirror
He was featured in the Dark Mirror. During the Battle, his armor was crushed by a Toa of Iron and his essence was dissipated by a Toa of Plasma.

Appearances

 * Dark Mirror(parrelel)
 * The Mutran Chronicles(mentioned)
 * BIONICLE World

Source