Bionicle stands for "Biomechanical Chronicle" and is Lego's first original saga. It begins with six heroes called toa fighting for peace, and win against the evil Makuta. They are transformed in a battle against a new evil, the bohrok, and the first evil comes back with his sons, the Rahkshi. Another toa is discovered and Makuta is defeated once and for all. The village chieftans tell the toa a tale of Metru-Nui, their past, and how they were once toa. At Metru-Nui a matoran villager is a traitor, and plans to destroy Metru-Nui, a super advanced city. Then everyone fled to Mata-Nui, etc.
"I must face him alone." - Takanuva, the seventh toa. From Bionicle, Mask of Light.