|Primary Residents||Matoran; Skakdi; Kuai; Makuta|
|Location||Southeast of Tunakai Nui|
Gahru Nui once was a single island, with many pristine lakes and lush forests. Many Rahi thrived there. When the Makuta were still good, Makuta Cortrivu chose this place to build his laboratory for creating new species of Rahi. One day, the island's huge volcano, Mt. Termihi, erupted with such a force that the intire volcano exploded, sending lava and ash everywhere. Mt. Termihi was connected to the very roots of Gahru Nui, so when it erupted, the roots broke and Gahru Nui started splitting and drifting away rapidly, although its drifting as slowed down almost to a standstill. When the sections of Gahru Nui floated in different directions, its climates changed, turning forests to fields of ice, lakes to desert valleys. Many Rahi died out because every thing was covered in ash for the next 80 years. Cortrivu's lab was destroyed by lava floes, and Cortrivu fled to Mangaia.
100 years after the eruption of Mt. Termihi when all the ash had cleared, guardians of the Kanohi Agnoka, called 'Kuai', came to Gahru Nui to protect the mask after Keighvin had givin it back to them. About this time, Makuta Teridax overthrew Makuta Miserix, and Cortrivu was returning to Gahru Nui for a new mission: create powerful fighting Rahi to seek out and destroy beings of the element Light. The Kuai were afraid that Cortrivu might get hold of the Kanohi Agnoka so they gave it to the Great Being that created it, who transformed the mask into six Element Stones that, once united in a specific location, would return the Agnoka back to its Kanohi form. But Cortrivu had heard of the Agnoka's great power, and ordered an lesser Makuta, Venetraze, to find it. Venetraze wasn't exactly what you would call willing, since Cortrivu had mutated him earlier because he failed one of his missions.
One of the Kuai Guardians, Mekiru, went to Cahlra Nui to tell the Toa Avohkii about the Agnoka. Before he could finish explaining where to unite the six stones, a Kuasli-bearing Makuta suddenly appeared before them and killed the Guardian, and accidentially teleported Tritau to Karda Nui with his Kualsi when he meant to teleport Iymouvu. Iymouvu then overwhelmed him with her light powers and thus killing him and damaging his Kualsi. Iymouvu then went searching for Tritau trying to use the damaged Kualsi, while the remaining Toa Avohkii started their journey to Gahru Nui.
When Lord Zidoran outlawed the Black Assasins from Obsidia, the Black Assasins went across the ocean to Gahru Nui, and then learned of the Kanohi Agnoka. They started searching for the stones. Most of them where ambushed and killed by the Kuai because they thought that they were the only ones on the island.
When all but three members of the Toa Tegen were killed by a sentient acid cloud, the remaining being Kier, Shagatiku, and Tiekess, most of Tiekess's armor had been dissolved by the cloud, and she was barely alive. She was teleported to Daxia by the acid cloud and was found by Johmak. Then she was rebuilt by the Order of Mata Nui and sent to Gahru Nui to to help the Toa Avohkii unite the Element Stones.
During the First and Second Crumaki Wars, Cortrivu created the Crumaki in his new laboratory. He created them out of Rahi that were twisted and deformed from the ash and smoke from Mt. Termihi's eruption, mutated them into new species with his Kanohi Rahyetth. He also created the Crumaki-Kal and Crumaki-Ivu.
- Gahru Nui's name means "Great Flooded Land."