Hydraxon was originally in the Hand of Artakha. After its disbanding, he joined the Order of Mata Nui, and recruited fellow former Hand member Axonn into the Order. One of Hydraxon's first Order missions was to train the Toa Mata. Hydraxon did that using multiple methods, including physical assaults, challenging their Three Virtues, and releasing his Energy Hound, Spinax, on the Toa, though he claimed the latter was a training exercise for the hound, not the Toa. While conversing with Gali, he mentioned his next assignment, and became very grave about it and his next trainees. Upon finishing his training with the Toa, he became the Pit's jailer. As a Pit Jailer, he was helped by a few guardian robots and Spinax, but later gave it to one of the Maxilos robots. Hydraxon was severely injured when the Great Cataclysm hit the Pit, shattering its dome and causing a cave-in. Takadox came across the wounded Hydraxon and killed him. His body remains buried under tons of rubble, somewhere in the original Pit.
A Po-Matoran named Dekar was making his way back to the city of Mahri Nui from a nearby sea cave, running short of air after his experiences with the Kanohi Ignika and escape from the Barraki. Suddenly, he began to have visions of another figure in a totally different environment. Though he did not realize it, he had been transformed into a near-perfect replica of the late Hydraxon by the Mask of Life. The mask had decided it needed protection, and Dekar was the only being in the area besides the Barraki. With Dekar's mind and memories completely buried under Hydraxon's, the newly reborn Hydraxon continued his journey, although with a different reason. Believing every living being except himself, Rahi, his guard robots, and Energy Hounds to be Pit escapees, Hydraxon recruited one of the Maxilos robots and embarked on a quest to capture everything in the open ocean. Upon arriving at Mahri Nui, Hydraxon spotted and promptly captured the Toa Mahri named Matoro, threw him in a jail cell, and introduced him to Maxilos and Spinax, whom he was entrusting to the robot. He then left the cell, unaware that Maxilos had been taken over by the essence of Teridax. Hydraxon later spied on a Barraki strategy meeting, defeated the powerful Nocturn in single combat, and came into possession of the Mask of Life. Remembering a faint memory from Dekar, he opened fire on the mask with his Cordak Blaster, believing it not safe for it to be in the Pit. Toa Hahli redirected the Cordak mini-rocket with a riptide and began a fight with him.
Their fight concluded when