Bionicle 2: Legends of Metru Nui (2004)

Six Matoran from the city of Metru Nui are chosen by Toa Lhikan to become mighty Toa Metru. However, all is not well in the city, as Matoran are vanishing, Turaga Dume is acting strangely, and Toa Lhikan is captured by a pair of menacing Dark Hunters. Toa Vakama and his five brave companions must find their mask powers, dodge the ruthless Vahki enforcers, and try to free Toa Lhikan, whilst revealing Metru Nui's darkest secret.