2004 was the fourth year of BIONICLE. It was a flashback year telling the story of the Turaga of Mata Nui when they had been Toa Metru on the island of Metru Nui. It focused on their conflicts with the Morbuzakh, the Vahki, and Makuta Teridax.
Six comics were released, as well as six books under the series title BIONICLE Adventures. A second movie, BIONICLE 2: Legends of Metru Nui, was also released this year. The total number of sets released in this year was twenty-four.
One thousand years before the 2001-2003 storylines took place, in the island city of Metru Nui, a vicious sentient plant known as the Morbuzakh was slowly taking control of the city. Matoran were disappearing, and many places were becoming too dangerous to live in. But Toa Lhikan, the city's last living Toa, created six Toa Stones and delivered them to six Matoran: Vakama, Matau, Nokama, Whenua, Onewa, and Nuju, one from each of the six metru of the city. When he delivered Vakama's, two Dark Hunters named Nidhiki and Krekka attacked and kidnapped Lhikan. Shortly after this, Turaga Dume (actually Makuta Teridax in disguise) entered Vakama's forge and asked him to make a Mask of Time before the upcoming Akilini game. When Vakama and the others used their Toa Stones at Ga-Metru's Great Temple, they became the Toa Metru. Toa Vakama told the others of a vision he had: they must find six Matoran: Nuhrii, Orkahm, Vhisola, Tehutti, Ahkmou, and Ehrye, as well as the six Great Disks, the locations of which were known by the Matoran.
They split up and each went to their own metru to find the Matoran with the same element as them. All of the Matoran save Ahkmou (who was trying to hide, not be rescued) had been trapped by Nidhiki under something (or in Vhisola's case, hanging off the side of a building) and the Toa Metru managed to save them, some of them meeting with Vahki that wanted to capture and interrogate them. When they all met up again, they determined that one of them was a traitor: Ahkmou.
The Toa Metru and the Matoran of their elements split up into three groups: Vakama, Nuhrii, Onewa, and Ahkmou on one team, Whenua, Tehutti, Nuju, and Ehrye on another, and Nokama, Vhisola, Matau, and Orkahm on the last. After contending with Vahki, they found the Great Disks and went to destroy the Morbuzakh with them. The Toa Metru headed to the Great Furnace in Ta-Metru where they deduced the Morbuzahk's king root must be. The Matoran combined themselves into a Matoran Nui to allow the Toa Metru to get past the rapidly-sprouting Morbuzakh seeds in the Great Furnace, and they passed to fight the king root. After exhausting their elemental energies, they had to use the Great Disks, and they destroyed the king root.
They headed to the Coliseum to present themselves to Turaga Dume. But on their way, a Matoran named Nuparu informed them of a leak in the Archives of Onu-Metru. So the Toa Metru headed there to plug the leak, planning to present themselves to Dume after doing so. In the Archives, they encountered many Rahi and Rahkshi, all of them hostile. When they reached the Fikou Web, a large tunnel system in the Archives, they split up and encountered a shapeshifting Rahi called Krahka that attempted to become them and turn them against one another. Finally, they tricked her, and she attacked them using all of their forms combined into one. Using their powers together, they defeated her, but Vakama allowed her to escape.
Finally, the Toa could present themselves to Dume. But when they did, he did not believe that they are Toa. He puts them to the test by making them try to cross the Sea of Protodermis. They failed, and Dume sent Vahki after them. Onewa, Nuju, and Whenua were captured, while Vakama, Nokama, and Matau escaped. The Toa who escaped left through a chute, and found a Vahki Transport headed for Po-Metru. On it, they found strange pods. Vakama had another vision that told him Matoran were inside. In Po-Metru, they had an encounter with Nidhiki and Krekka, who they escaped using Nokama and Matau's newly-discovered mask powers of Illusion and Translation. Then they headed for the prison where the other Toa are being held.
Meanwhile, the other Toa had met Lhikan, who had since become a Turaga and had taught them how to use their mask powers. When the two groups of Toa met up, they had to fight more Vahki, and Lohrak. Finally, they found a Vahki transport, which they and Lhikan rode to the Coliseum. There, they witnessed the Matoran of Metru Nui being packed away into the pods they saw earlier, and Turaga Dume revealed himself to be Makuta. He absorbed Nidhiki and Krekka and Nivawk, his pet bird Rahi, into himself and transformed, absorbing the energy of Metru Nui and putting the Great Spirit Mata Nui to sleep. Vakama attempted to fight him, and discovered his mask power in the process. He also tried to use the Mask of Time that he made from the Great Disks, but in the end, Turaga Lhikan had to sacrifice himself, and the Toa sealed Makuta in solid protodermis.
Taking six of the Matoran pods, the Toa Metru then headed away from Metru Nui and past the Great Barrier, heading for another island for the Matoran to live on. Eventually, they were attacked by giant sea Rahi, and saved by a Matoran named Mavrah, who was using the Kralhi, banished from Metru Nui after being replaced by Vahki, as his servants. The Kralhi attacked them, and a large battle ensued in which the path back to Metru Nui was sealed off, one of the Matoran pods was lost, and Mavrah drowned. They continued on, reaching a large island that they decided to bring the Matoran to. After exploring the island, they returned to Metru Nui, encountering several mutant beasts on the way.
Along the way, they encountered a Morbuzakh prototype called the Karzahni, named after the place in Matoran legend where bad workers were sent as punishment. It wanted them to get it Energized Protodermis to transform it into something strong enough to destroy Makuta, the one who abandoned it for being too smart. Being that Nokama was poisoned by an attack from the Rahi Nui and was dying, and the Karzahni had a cure, they had no choice but to comply with its wants. After an encounter with a being made of energized protodermis, they returned. The Karzahni was destroyed by the protodermis, but not before healing Nokama. So the Toa Metru began to make their way back home for the rest of the Matoran.
- BIONICLE Adventures 1: Mystery of Metru Nui
- BIONICLE Adventures 2: Trial by Fire
- BIONICLE Adventures 3: The Darkness Below
- BIONICLE Adventures 4: Legends of Metru Nui
- BIONICLE Adventures 5: Voyage of Fear
- BIONICLE Adventures 6: Maze of Shadows
- Comic 16: Toa Metru!
- Comic 17: Disks of Danger
- Comic 18: Seeds of Doom
- Comic 19: Enemies of Metru Nui
- Comic 20: Struggle in the Sky
- Comic 21: Dreams of Darkness
Movies and Animations
- Toa Metru
- 8601 Vakama
- 8602 Nokama
- 8603 Whenua
- 8604 Onewa
- 8605 Matau
- 8606 Nuju
- Illustrations included inside the "The Darkness Below" book showed how to make the Krahka form of all six fused Toa Metru.
- Vakama, Matau and Onewa could be combined to make a Kralhi.
- Nokama, Whenua and Nuju could be combined to make a Kraawa.
- Each set came with a card that contained a Konaka code and was part of an instant win contest in which winners would recieve either a golden kanoka disk, a collection of BIONICLE comics, or an ultimate gaming system.
- Titans & Warriors/Rahi
- 8811 Toa Lhikan & Kikanalo
- Contained a Toa Metru style set.
- 8623 Krekka
- 8622 Nidhiki
- 8621 Turaga Dume and Nivawk
- Contained a Box set style Matoran.
- 10202 Ultimate Dume
- Contained Krekka, Nidhiki, Nivawk, and an exclusive mask.
- Contained Instructions to make Ultimate Dume.
- Nidhiki and Nivawk could be combined to make a Lohrak, instructions were not included with this set.
- 8811 Toa Lhikan & Kikanalo