Nuva Symbols

The Nuva Symbols contain the Toa Nuva's power. If they fall in the hands of someone that does not respect the Toa, the Toa will lose their powers. The Bohrok-Kal exploited this in an attempt to free the Bahrag. The Toa Nuva also had a mental connection to the symbols, allowing them to pour their energy into the Bohrok-Kal, thus overcharging them.

The Nuva Symbols are the keys for the Nuva Cube, a lock to the Bahrag's prison.

The Toa Nuva likely took their symbols with them when they evacuated the Great Spirit's body

Trivia

 * The Nuva Symbols were made in Artakha, but in the comics, it says that each one was found or created somewhere in Mata Nui.
 * There are six Nuva Symbols, and their elements are Fire, Water, Air, Stone, Ice, and Earth.