The Pit

The Pit is the place where the Order of Mata Nui banishes the world's most vile beings. It was once in an underground cavern, but the Great Cataclysm caused the dome that surrounded it to be destroyed, exposing The Pit to the ocean on the planet's surface. The Pit flooded and the inhabitants escaped into the ocean, where something in the water immediately mutated all immersed in it into aquatic forms. This allowed the prisoners to survive but - no longer able to breathe air - they were unable to escape to the surface, so the sea has become effectively an extension of The Pit. Some time later, the island of Voya Nui floated into that region of ocean, and Mahri Nui sank to a point where it is resting on The Pit's upper reaches.

Some current inhabitants of The Pit are a group of warlords called the Barraki, the Matoran leaders of Metru Nui's "Great Disruption", and now Brutaka. All other prisoners have scattered across the sea bottom, most of them becoming scavengers.