After the Toa Metru re-entered the city of Metru Nui on their mission to rescue to Matoran, the Toa quickly discovered that the entire city was shrouded in mist and strange webbing. However, due to the overconfidence of their leader, Vakama, the team was quickly ambushed and captured by the spider-like Visorak. Condemned to die by the Visorak king Sidorak and his repulsive viceroy, Roodaka, the Toa were saved by six bizarre, Rahkshi-headed freaks called Rahaga. But the venom of the Visorak had done its damage - the six Toa had been mutated into grotesque half-Toa, half-beast monsters called Toa Hordika!