Barnax is a purple being who resembles an angler-fish. He likes to eat cheese, and carries a double-edged spear and a Thornax launcher. His brother is QQQ.
Back in the Matoran Universe, Barnax was a minor warlord, but he was driven from power when Blackout and Malygos took over. He travelled the galaxy alone, occasionally seeking treasure, but mostly buying up exotic cheeses. On one occasion, having run out of money to buy cheese, he travelled to Atlantis, looking for a treasure that had been hidden near there. He made an alliance with Blackout, and then dug up the treasure.
In the far future of the Original Universe, Barnax joined F-Klak's forces in exchange for cheese. He was drafted into Mirage's team on Teruga Prime, where they drank a lot while Mirage did all the work. At one point, they picked up Catalyx's remains at a junkyard, and Barnax used his knowledge of robotics to piece the being back together. However, the damage to his brain was too extensive, leaving him amnesiac. Barnax uploaded a battle-droid software package to his brain and left it at that.
Later, when Mirage was asked by Tox, Speaker of the Terugan Parliament, to commit a terrorist act to give the government an excuse to declare war on neighboring planets, Barnax helped by planting bombs around the Town Hall. The team then left to meet with F-Klak, where they discussed the Earth government's defiance and decided to overthrow the local dictator, Khan Noonien Singh. Barnax revealed that the planet was equipped with only one communications satellite (which the government "bought" from his brother), and could easily be made to go dark for the duration of a revolution.