Nui Stone

"The Nui Stone is active, where a Toa Stone is passive. It doesn’t wait for you to give it your energy – it takes it. Once activated, it will absorb minute amounts of energy from any Toa within a 3000 Kio radius, so slowly and surely that it won’t be noticed until it’s too late. Then that energy can be absorbed by a living being – can you imagine? One being with the power of dozens, maybe hundreds of Toa, or more?"

- Toa Tuyet to Toa Lhikan

The Nui Stone was a powerful one-of-a-kind artifact in the Bionicle universe, with the aggressive tendency to slowly absorb Toa energy from all Toa in a 3000-kio radius. Whoever touched it would gain its power. It glowed red with energy and heat.

Creation
Long ago, the makers of the Nui Stone created it, but knowing its power, decided to destroy it. However, before they could, it was stolen from them and passed around for years.

Tuyet's Home Island
At some point, the Nui Stone ended up on the home island of the Water Toa Tuyet. The Dark Hunters came after it, but they arrived to find that the stone was gone...as was Tuyet. Naturally assuming she had taken the Nui Stone with her to Metru Nui for safekeeping, they went there.

Metru Nui
On Metru Nui, Tuyet hid the Nui Stone in her dwelling and kept it a secret for a long time. Eventually, deciding the Dark Hunters would not stop looking for her if someone did not stop them, she began to murder Matoran, claiming to Toa Lhikan and Nidhiki that it was a 'countdown' by the Dark Hunters, and that she had seven days to give them the Nui Stone. While Dark Hunters were indeed searching for her, they had no idea of such a countdown. Lhikan realized that Tuyet had been the murderer, and used his heat-sensing abilities to locate where she had hidden it.

Tuyet took the Nui Stone back from Lhikan and used it to empower herself, claiming that she would become the 'ultimate solution' and do what the League of Six Kingdoms tried to do. Lhikan and Nidhiki defeated her, however, and Lhikan destroyed it.

Trivia

 * The Nui Stone was first revealed in the BZPower-exclusive short story 'The Many Deaths of Toa Tuyet'.