Karda Nui is a large subterranean world directly below the Southern continent. It is quite literally Mata Nui's heart, and it is where all of the energy essential to Mata Nui's health is produced. This energy is typically sent to Metru Nui and redistributed from there as needed. The Av-Matoran originally lived here, but later migrated to the caves just above Karda Nui when the energy storms began.
As long as Mata Nui is healthy, this region should not be safe to visit.
