BIONICLE Legends 7: Prisoners of the Pit

Prisoners of the Pit was the seventh Bionicle Legends book and came out in 2007.

Story
A wisp of smoke floated through a stone tunnel down to the Pit. It was actually the Makuta of Metru Nui, removed from his armor. He was planning to get things done for himself for once, after the failure of the Rahi, Bohrok, and Piraka to defeat the Toa. Elsewhere in the stone tunnel, the Toa Inika were struggling to stay alive against a tribe of Zyglak. The tunnel began to crack and flood, and the Toa decided to take their chances in the ocean. There they discovered the cause of the crack: a giant Venom Eel. Attracted to the light of Jaller's swords, the venom eel headed for the Toa. However, at that very moment, the Mask of Life let out a huge flash of light and energy in response to the Barraki Pridak grabbing it from the Matoran Dekar. The Toa Inika could detect that the mask was calling out for help. They were changed by the mask, mutated into Toa Mahri. They were left unconscious from the energy surge. Meanwhile, the Barraki were surprised to be alive after the energy burst. Kalmah found Pridak clutching the Ignika in a state of insanity, with a large crack running through the mask. Takadox noticed the unconscious Toa Mahri and waited to see the venom eel eat them. Elsewhere, Dekar was almost out of air and nearly dead. But the Mask of Life saved him, recreating him as Hydraxon, the long-dead jailer of the Pit.

When the Toa Mahri woke up, they were forced to fight the giant venom eel. They discovered that their Kanohi had changed powers, and using the new powers, they defeated the eel. They then tried to talk to the citizens of Mahri Nui, but the Matoran there did not trust them, believing they were prisoners of the Pit. Defilak allowed Matoro to enter the city (though he could not, as the Ignika's transformation kept him from breathing air), and told the other Toa to free the Fields of Air of the Keras crabs invading it. Before they had to do anything, the Keras moved aside, only for the Toa to realize that it was because the Barraki had found them.

The Barraki took the Toa prisoner, and meanwhile, Matoro was taken prisoner by the recreated Hydraxon. Hydraxon introduced Matoro to Maxilos and Spinax, two guards. Maxilos revealed to Matoro that he was in truth the Makuta, but was on Matoro's side.

The Barraki, meanwhile, had decided to wait until the Mask of Life was destroyed by the Pit's Mutagen and then use the leaking energy to restore themselves to their forms before being mutated. They gave it to Nocturn, another prisoner, for safekeeping. The Toa Mahri escaped from their cells using their mask powers, and a Hahnah Crab began following Jaller. Kongu unintentionally unleashed a gigantic ancient sea Rahi with his Zatth.

The Toa Mahri found several Cordak Blasters in a cave. Each Toa took one, save Kongu, who took two. They then returned to Mahri Nui and gained the Matoran's trust to an extent. Matoro joined up with them, pretending that Maxilos was their ally. Meanwhile, Nocturn discovered that while he holds the Mask of Life, everything he touched died. He put the mask down for a second, and a gadunka jumped under it for shelter. It slowly began to be enlarged, but Nocturn had already walked off with the mask, looking for Ehlek to tell him about his newfound power. Back with the Toa Mahri, Maxilos suggested that the Toa split up.

On his way to the squid farm, Carapar noticed that the revived venom eel was fighting with the monster Kongu had awakened. At the squid farm, the Barraki decided that the Toa must have stolen the Mask of Life when they escaped, and they split up to catch them and retrieve the mask. Mantax attacked Hahli, only to find out that the Toa Mahri had no idea where the mask was. Jaller and Kongu stumbled upon several hatching squid eggs, and ended up making a deal with Kalmah and Carapar to avoid being killed by the newborn squids. Nuparu and Hewkii were attacked by Ehlek and thrown into a venom eel nest. They escaped using their Cordak blasters. Matoro and Maxilos met with Pridak and Takadox and started a battle: Pridak's army of Takea against Matoro's Tryna-reanimated sea monsters. A war began among the Barraki after that event.

Several hours later, the Toa Mahri returned to Mahri Nui, although Hahli was nowhere to be found. A Ga-Matoran reported then that Hahli was seen leading a group of manta rays. Meanwhile, Nocturn met up with Hydraxon and was defeated by him. Hydraxon then decided to destroy the Mask of Life, launching his Cordak blaster at it.

Elsewhere, on Metru Nui, the Toa Nuva were sneaking to the Great Temple for a message that Axonn had told them about. They found such a message, written on paper much to their confusion. It was a list of things needed to be done before Mata Nui could be awakened. The first thing was for the Bohrok to complete their mission. Thus, the Toa Nuva traveled up to Mata Nui and freed the Bahrag queens. As soon as they did so, the Bohrok woke up, ready to continue their mission.

Characters

 * Barraki - Takadox, Mantax, Carapar, Pridak, Ehlek, Kalmah
 * Toa Mahri - Jaller, Hahli, Kongu, Matoro, Hewkii, Nuparu
 * Toa Nuva - Tahu, Gali, Lewa, Kopaka, Pohatu, Onua
 * Matoran - Defilak, Dekar
 * Nocturn
 * Hydraxon
 * Maxilos/Makuta of Metru Nui
 * Spinax
 * Gadunka
 * Bahrag queens
 * Bohrok
 * Zyglak