With one final duty to fulfill before they can build their new home on the island of Mata Nui, six great Toa heroes return to Metru Nui and find their once-glorious city shrouded in shadows and overrun by a sinister army of spidery, web-slinging Visorak. Mysteriously transformed into strange beast-like creatures know as Toa Hordika, the Toa realize their mission to recue the stranded Matoran - held captive by dark powers - will be anything but easy.