Heart of the Visorak

The "Heart of the Visorak" was a golden crystal that had something to do with the Visorak. Pohatu and Onua found this artifact as part of the Toa Nuva's quest to awaken Mata Nui. When placed on the ground, it summoned all Visorak to it's location.

Dwellers
In the Dwellers in Darkness story, a blue figure gave the heart of the Visorak to The Toa Mahri, Jaller, Hahli and Nuparu took it to Artidax. They found Takadox! Takadox put them in a trance, he stole the boat. The Volcano was about to erupt. They placed the heart of the visorak down then ran, and swam.