The Pit was the name given by the Order of Mata Nui to its place of imprisonment for those deemed beyond redemption. The Pit was a series of cells within a dome, overseen by Hydraxon and guarded by Maxilos and Spinax. Inmates were transported there by Botar and included the worst criminals in the universe. The prisoners broke free when the Great Cataclysm shattered the walls of the Pit, and they escaped into the black water of the ocean floor outside the dome. The mutagenic properties of the seawater severely transformed all of the inmates (except Nocturn) and made it so they could only breathe water. None of them could survive on land anymore. Because their escape into the black water outside the dome hardly resulted in freedom, they came to know the surrounding ocean area as the Pit as well. A few centuries later, Mahri Nui sank into the Pit.
Toa Tuyet was condemned to the Pit for the unpardonable crime of slaying Matoran, those she was intended to protect.
Originally, the Order of Mata Nui intended for the Pit to be a place where prisoners would live out their days for all time and be forgotten.
The Pit came to lie beneath a saltwater ocean, the same ocean which surrounded the islands of Voya Nui and Mata Nui. However, in the depths of Mahri Nui and the Pit, the waters were quite different, having both corrosive and mutagenic properties that affected both living and non-living things. It was an extremely difficult place in which to survive. Some beings, like Botar, had a natural immunity to the environment of the Pit. Most, however, needed to take special precautions against prolonged exposure to the waters.
At one time, the Pit was an enclosed area well to the south of any known island. It was a prison for those the Order of Mata Nui deemed beyond redemption. The Great Cataclysm shattered the Pit's enclosure, releasing its inhabitants into the waters outside of it. The inhabitants came to dwell in the murky, dark waters beneath Mahri Nui, longing for revenge on the universe that shunned them.
The Pit contained the waters beneath Mahri Nui, which were known as the black water.
The Pit was home to many bizarre creatures, including the sea squid.
As of story year 2008, the Pit was a dark, cavernous chamber. The Barraki Pridak, Kalmah, Mantax, and Ehlek were kept in the lowest tier of cells, which was accessible with an iron ladder.
The Pit was the maximum security prison run by the Order of Mata Nui which housed only the worst criminals.
Ages ago, the Order of Mata Nui established a domed prison for the very worst criminals in the universe. Guarded by Hydraxon and the Maxilos series of robots, it was believed that no one could escape from it. The Order named the place "the Pit." Over time, it held the Barraki warlords and others.
- BIONICLE Legends #1: Island of Doom included the excerpt: "The reflections of torchlight turned their armor red and gold, but they were not the pure, clean colors of a Toa of Fire – no, they were the fearsome hues of creatures from the pit." This book was written before the 2007 story was planned in detail or its locations were named.
- The Black Water
- The Cord
- Fields of Air
- Mahri Nui
- Mahri Rock
- Octo Cave/Squid cave
- Pillars of Salt
- Razor Whale's Teeth
- Salt Mountain (?)