|Location||West of Mata Nui, North of Laksuj-Konom|
|Size||Includes Catacombs, ruined city, Yudia mountains|
Yudia Nui was created to the north and became frigidly cold, so many Ko-Matoran settled here from other islands. Yudia, in the Matoran language, means "Knowledge." Ko-Matoran claimed it was "a paradise like no other, its future was bright." Later, more Matoran of different types flocked to Yudia Nui, utilizing the Snow Huts imported from Kiel.
The Dark Times
When the World Schism appeared on Gatris Nui, many Ko-Matoran foresaw the end of the world. Matoran from Nui Marsh and Gatris Nui went to Yudia Nui for safety, since they thought that the Ko-Matoran would know what to do. When they had no ideas, some began digging underground, forming a collection of caves that extend as far as Nui Marsh known as the Catacombs. Many people lived here until the Nui Orbs were created, and a strange Matoran from Gatris Nui hid a large Nui Orb on Yudia Nui.
The Nui Orb crises
Makuta himself once traveled to Yudia Nui in search of the Nui Orb hidden there. He battled with the lone protector of the island, Toa Yudia,on the middle of the island. The battle continued until one of their energy blasts uncovered a Nui Orb, which sat on a stone pedestal. Both of them touched it, which sent it flying and breaking on the ground, releasing a huge blast of energy that turned the island from a winter wonderland into a nuclear wasteland. The part of the island where they fought was completely obliterated, with a large lake now in its place. The Matoran say the explosion shook time itself, blackening the water with ash and the sky gray with smoke, the ground on fire. The Matoran were safely in the catacombs at the time, evacuated by Toa Yudia himself.
No one has gone to Yudia Nui much anymore after the devastating Nui Orb crises. The Matoran still live in the Catacombs, earning a living by mining the rich, solid protodermis from the ground below Yudia Nui. Instead of going to the surface and trading form there, the Matoran use the Catacombs to travel to Gatris Nui, and trade from major ports there. Due to the invasion of Gatris Nui recently, the Matoran of Yudia Nui have made the catacombs go further to Nui Marsh, where they now trade. Yudia Nui currently has no Toa.