The Toa Metru return to Metru Nui to save the rest of the population, after finding a new land where they believe the Matoran can live peacefully. The city they come back to bares little resemblance to the Metru Nui of old; it is an industrial jungle full of wild beasts and fallen infrastructure. Earthquakes have ravaged the buildings, large webs surround structures, and the dangerous Rahi roam the streets. the deadly Visorak have taken over Metru Nui. When the Toa Metru confront the Visorak fighters, they are injected with a dark poison that radically changes them into Toa Hordika: half hero, half beast. This new dual nature forces them to fight not only their enemies, but also the dark side that has been distilled within them. It is up to the Toa Metru to save the city of Metru Nui from the Sidorak, the Visorak king, and his sinister viceroy, Roodaka; and to save each other from themselves.
