2003 - The Bohrok-Kal Strike / Mask of Light

Following the defeat of the Bahrag Queens and the Bohrok's return to their hives, the Toa Nuva return to their villages to help the Matoran in the rebuilding process after the damage the swarms caused. However, six new elite Bohrok, the Bohrok-Kal, have arrived on Mata Nui with the intention of releasing the Bahrag from their prison so they can unleash the swarms once again. 

The Kal each steal the Toa Nuva's symbol tablets that grant them their elemental powers, leaving the heroes greatly outmatched. Relying solely on their mask powers and combat skills, the Toa chase the Bohrok-Kal all over Mata Nui and eventually find them in the Bahrag's underground nest. The Kal defeat the Exo-Toa guards with ease before attempting to combine all six Nuva symbols to re-awake the Queens from their prison. 

Before the tablets join, Tahu unleashes a secret weapon; the Kanohi Vahi - the legendary Mask of Time - to slow down time around them so the Toa can retrieve their tablets. The Toa Nuva then use their connections to their symbols to feed energy into the elite Bohrok, making them believe that their power alone can cleanse Mata Nui. However, the Kal's powers soon run wild and eventually destroy them. 

Clean-up begins once again in the island's villages, even to the extent of creating a brand new Kolhii field in Ta-Koro. The Toa Nuva exit the nest, and after hiding their retrieved tablets at secret locations, enjoy a new time of peace on Mata Nui. But worse foes await the Toa and the Matoran…

Weeks later, Takua and fellow Matoran Jaller discover a great Kanohi mask hidden under their village of Ta-Koro. After playing in the Great Kohlii Tournament in the village's new field, they take it to the Turaga who confirm it is the Kanohi Avohkii - the Mask of Light - prophesied to be worn by a seventh Toa with the elemental power of Light who can defeat the Makuta for good and begin the process of reawakening Mata Nui. 

Learning of Takua and Jaller's mission to find the seventh Toa, Makuta unleashes his "sons"; six Rahkshi - robotic suits of armor powered by slug-like Kraata created from his essence - to track down and kill the herald before the seventh Toa can be found. The Toa Nuva battle the Rahkshi all over Mata Nui, who level the villages of Ta-Koro and Onu-Koro in their search for the herald. 

The Rahkshi find Takua and Jaller at Kini Nui as a final confrontation between the Makuta sons and the Toa endues, killing Jaller in its last moments. The death of his friend convinces Takua that he is the true herald. Donning the Avohkii, he transforms into Takanuva; the Toa of Light, and travels underground to Lair Mangai, followed by the rest of the Mata Nui populace. 

Takanuva confronts the Makuta and the pair dual in a game of Kohlii for the fate of Mata Nui. Claiming his victory, Takanuva attempts to take off the Makuta's Mask of Shadows, but they both fall into a pool of energized protodermis and re-emerge as the fused being Takutanuva.

Takutanuva lifts the gate to an underground city for the Toa, Turaga and Matoran enter and manages to revive Jaller, before the weight of the gate crushes him. The Turaga retrieve the intact Avohkii from his demise and use it to revive Takanuva, whereas the Makuta's fate is unknown. Preparing to journey to the city, the Turaga reveal its name as Metru Nui - the Matoran's original home - and go on to reveal that the Toa Nuva are not in fact the first Toa.