Mangaia lies beneath the Kini-Nui. It is reached by entering a stairwell directly below the Suva Kaita; the Suva opens up to reveal a deep black pit, and not all are fortunate enough to be given the opportunity to use the stairs. Having reached the bottom of this pit, beings will find themselves on a metallic elevator which transports them down to a lower, fog-filled cavern.
It is in this cavern that the Manas were located, though now they have all been slain by the Toa Maru on their way to battle Makuta.
The lair itself is massive, containing several rooms connected by vast corridors. Besides the main room where Makuta seems to reside, only a handful have been revealed. Many seem to be laboratories or transformation chambers, such as the one in which Echelon's mask was Infected (containing a vat of Kraata) or the one where Lantz was transformed into a Toa Hordika. Heuani's personal chambers are also believed to be found somewhere herein.
The main hallway that leads to Makuta's central chamber from the Manas' atrium is of accordingly large proportions, carved from dark stone and flanked with colossal pillars that stretch up into the blackness. It was here that the Toa Maru fought and prevailed over their Shadow-corrupted predecessors.
The chamber in which Makuta resides is vast and stretches away into shadow. A hellish red light illuminates the centre of the room, and the dark entity himself.
Makuta’s former lair is a maze of dark passageways and huge chambers. It has several entrances: one below the Suva Kaita, one through the Suva Nui in Le-Wahi, and six long Dark Walk tunnels branching straight from a central chamber in Mangaia to the doorsteps of each Koro are some to name. Even though the dark artifacts that used to inhabit the chambers of the caverns – many of which were unspeakable horrors – have all been long since destroyed or cast into the sea by the Toa Maru, a distinct air of danger still lingers down here. Lights carried by those either brave or stupid enough to descend into Mangaia seem to have less effect in its passageways than in other dark places, though there are some chambers illuminated by blood-red lightstones.
Makuta’s Rahkshi, no longer under his control, still tend to gravitate towards the dark places of the island, and there is nowhere darker than Mangaia. Several wild Rahkshi stake out their own caves and attack any who get too close, or who are unfortunate enough to pass them in the stony corridors. Some rooms are blocked behind thick doorways; whether such doors are viewed as invitations or as warnings varies on the explorer in question, but ominous sounds from behind them tend to drive most would-be enterers away. Sinister echoes seem to come quietly from everywhere.
The main attraction that compels surface dwellers to enter Mangaia is what is assumed to be Makuta’s Vault.