Karzahni

Karzahni is a name applied to three things in LEGO's BIONICLE line, the Morbuzakh prototype and the lord of the Matoran underworld and his domain.

The Ancient Being
Originally, in the past, an ancient being was the leader of a dark and terrible place called Karzahni. No one knows the ancient being's true name, so most call him Karzahni as well. Matoran who did not work well were sent there. (See Artakha for more info on this). Many consider this tale just a myth, however the Matoran Jaller encounters Karzahni in his own kingdom in the book Bionicle Legends #2: Dark Destiny. He has an old and sharp appearance, with armour that is spiked and a mask that is seemingly made of older masks patched together. Instead of having a loud roar-like voice, he spoke in whispers. He is so old that he does not even know of The Makuta or Mata Nui. The dark land he rules over is a very hot place, with the ground screaming at every step you take as well as ice cold flames. Matoran that were punished to this terrible place were driven mad to the point of merely becoming shells of their former selves, almost like zombies. Karzahni is also an incredible weapon crafter. He is the one who gives the Voya Nui Resistance Team their incredible weapons. This shows us that Karzahni is a portagonist that punishes the wicked.

Karzahni apparently was meant to repair the matoran and return them, but adopted new styles and began enslaving the matoran, and they stopped sending matoran to him. When Jaller and the others came, he thought that they were the usual lazy matoran sent by the others.When Matoro challenged him to make the worst vision ever, he was shocked by his own vision.

The Plant
In the book (and Game Boy Advance game) Maze of Shadows, the prototype of the Morbuzakh plant, which was created by Makuta, was found in Makuta's lair by the Toa. He had been named after the ancient leader Karzahni, and although he seemingly was destroyed by the Toa, in a dark cliffhanger the book noted a single sprig that seemed to have sprouted from the dead vines of the Karzahni, which had been fashioned into a new boat vehicle for the Toa. This sprig later grew into a new Karzahni, with all the memory and experience of the old. It was this Karzahni who revealed to Vakama the existence of the Order of Mata Nui.