Karzahni (DMU island)
Karzahni was located in its own dome south of Metru Nui in the Matoran Universe. It was once a place where Matoran from across the entire Matoran Universe were sent to be repaired, but Matoran sent there never returned, so Karzahni fell into legend as a hellish plane where captive Matoran were forced to work to their deaths. The fact that Karzahni's landscape was devoid of other life and filled with environmental hazards supported these legends.
In 3500 ADP, Takanuva travelled to Karzahni to intercept a Toa Empire convoy that was in the process of transporting the Kanohi Vahi to Metru Nui. Takanuva landed in front of the convoy and tried to trick its Toa escort party into surrendering the mask by claiming that Brutaka planned to steal it, but Takanuva's ruse fell through because one of the Toa had previously killed Brutaka. Because of this, the Toa arrested Takanuva and proceeded across Karzahni with him as a prisoner until the convoy was attacked by Lesovikk, who defeated the enemy Toa and rescued Takanuva. Takanuva and Lesovikk retrieved the Vahi and took an underwater chute back to Metru Nui.
Later, a Toa of Plant Life who was allied with the Toa Empire shouted "To Karzahni with you, Dume!" in response to Dume's claim that Tuyet had lied about the Toa Empire's purpose and had poisoned the minds of her followers.