BIONICLE Legends 5: Inferno

Inferno is the fifth Bionicle Legends book and came out 2006.

Story
These events take place over 100,000 years ago

Two Great Beings, having traveled across the world (including the realms of Artakha and Karzahni) arrive in the area that will become Voya Nui. Using their powers and tools, they construct the tunnels leading down to the Chamber of Life, placing traps inside as they do so. One of the Great Beings is revealed to have forged the Mask of Life, and both are wary of its power. Once their task is gone, they depart, knowing that in approximately 100,000 years the Kanohi Ignika will be removed from the Chamber, and that it will be replaced once its terrible power has been revealed.

These events take place after Bionicle Legends 3: Power Play

The Piraka come to a fork in the tunnel, with the path to the left blocked to them. Upon descending, they come under attack from the legendary Irnakk, who subjects them to their fears through the power of his Zamor Spheres. During the fight, Zaktan is drawn into Irnakk's mind, and realizes that Irnakk will disappear if he ceases to be afraid of him. Zaktan does so, declaring that he uses fear as a weapon just like Irnakk, and the giant vanishes.

Having witnessed through Matoro's mask power the battle between the Piraka and Irnakk, the Toa Inika come upon the same fork. Mysteriously, the left passage is unblocked instead of the right, and it appears to have been so for a long time. Elsewhere, Garan and the other members of the Matoran Resistance search for the missing Toa Nuva, knowing that the Toa Inika may need their help. The Toa Inika, traveling down the left tunnel, encounter an illusion of Toa Lhikan, who warns them to turn back before it is too late, they refuse to turn down a vital quest. Before the Toa Inika can learn more, he disappears saying that he wouldn't either "But look what happend to me."

Back at the Piraka Stronghold, Axonn and Brutaka continue their confrontation. The contest appears about even, since Brutaka has height and reach over Axonn but Axonn is stronger. Attempting to steal Brutaka's sword, Axonn is reminded that he gave it to Brutaka, and subjected to a painful electrical shock. Seeking victory, Brutaka uses his Kanohi Olmak to open a dimensional portal behind Axonn, which will not close until something passes through it, even if Brutaka is knocked unconscious.

Back at the volcano, the Toa Inika find themselves fighting illusions of Makuta, a Rahkshi Turahk, a Bohrok, a Bohrok-Kal, a Nui-Rama, and a Muaka. They triumph far too easily, and the seemingly dead beings turn into the Toa Nuva. The Toa Inika are disheartened, thinking the illusions to be real and wondering what they might do next with their awesome power. However, Jaller convinces the group that they have to press on despite their fears, and they agree. Moreover, the illusory Toa Nuva disappear, and Kongu realizes that they were illusions, having heard none of their thoughts with his Kanohi Suletu.

The Piraka continue their journey, contending with entrapping cylinders, a chamber filling with water, and jets of fire. They eventually escape, and set up an ambush for the Toa Inika. Outside, the Matoran come upon the Toa Nuva, badly weakened by a device which drains their elemental powers and enslaved by Antidermis. Utilizing their own Zamor Launchers, the Matoran free the Toa Nuva and help them get to the Piraka Stronghold, informing them of the existence of the Toa Inika.

Coming into a large chamber, the Toa Inika are greeted by the recorded voice of one of the Great Beings from the prologue. Proclaiming that the room they are in is the Chamber of Death, he informs them that in order for them to pass, one of them must die. Matoro volunteers, claiming that he is of the least use to the team since he is merely an interpreter and not a warrior, athlete, Chronicler, or inventor like the others. Matoro is destroyed by a beam of energy, but then his body is reconstituted. Going onward, the group is attacked by Protodax, only for the Rahi to be driven off by Umbra. Engaging the Toa Inika in battle, Umbra proves too powerful for them to defeat directly. Relying on Matoro, the Toa Inika use ice mirrors to reflect Umbra in light form until he is finally subdued.

Going forward, the Toa Inika find themselves locked in battle with the Piraka atop a bridge. The elemental energies of the Inika cause the structure to collapse, and the Piraka finally proceed to the Chamber of Life. Once there, they encounter none other than their long lost member Vezon. They discover that he has the Mask of Life, and he offers to give it to them if they kill Vezok. Despite the willingness of the Piraka to do so, Zaktan discerns that Vezon couldn't give them the Ignika even if he wanted to. Vezon then deploys the Spear of Fusion to merge Vezok and Reidak, creating a monstrous giant who obeys his commands by attacking the other Piraka.

The Toa Inika, having survived their fall from the bridge, agree that their only hope of victory over the Piraka is to fight with everything they can unleash. Back in the Piraka Stronghold, Axonn struggles to avoid both Brutaka's attacks and the ever-growing dimensional vortex. He warns Brutaka that his actions will bring Botar, whose name instills fear even in the sword-wielding giant. Driven to rage by his comrade's corruption, Axonn attacks with unbelievable force, shrugging off Brutaka's attacks as if they hadn't even hit him. In desperation, Brutaka looks to the vat of Antidermis, but Axonn destroys it before he can get to it. As it shatters, Axonn hears a voice besides Brutaka's crying out, deeper and more guttural. Bereft of his axe, Axonn manages to strike down Brutaka with a blast of power from his hands, and sanity returns to Brutaka's eyes just before he is knocked unconscious. Botar then appears and takes custody of Brutaka, and warns Axonn that any attempts to interfere with him will be met with Brutaka's punishment. Axonn vows to free his friend, and as all three Order of Mata Nui members leave, the vortex Brutaka opens is revealed to be a portal to the Zone of Shadow as Krahka and Tahtorak emerge from it.

Back inside the Chamber of Life, the Toa Inika arrive and confront Vezon. His powers, combined with those of Fenrakk, prove too much for them to contend with directly. The Inika then use their powers to force the two backwards into the lava, and Jaller prepares to go after them despite the knowledge that he will likely die. Before he gets the chance, Vezon emerges on the back of Fenrakk, now transformed into Kardas. As they struggle, Jaller realizes that the Ignika must be sentient, and has Kongu read its thoughts. Kongu discovers that the Mask of Life sensed their approach, and because of Matoro's attitude towards others selects him to be its new guardian. Beaming these thoughts into Vezon's mind, Kongu provokes the Piraka into a rage. Jaller then deploys Axonn's special Zamor Sphere, freezing Vezon and Kardas and allowing Matoro to remove the Ignika.

At the Piraka Stronghold, the Toa Nuva recover their masks and learn from the resistance just who the Toa Inika are, setting out to meet with their friends. On their feet again, the Piraka attack the Toa Inika, but the Mask of Life escapes them both, flying upwards through the catacombs. The Toa pursue, while the Piraka have a dispute involving the Spear of Fusion. Vezok wants Vezon to be fused with him once again, but the other Piraka destroy the spear, making it impossible. The pursuit of the Ignika continues, and it ends up traveling into the depths of Voya Nui bay. Attempting to retrieve it, Hahli is overwhelmed by immense pressure. Before the other Inika can do anything, a mysterious Matoran emerges from underwater and brings Hahli back to shore. After gasping out a cryptic plea for help and mentioning a city beneath the waters of the bay, the Matoran collapses in death.

The Toa Inika meet up with Axonn and the Toa Nuva, Botar having disappeared with Brutaka after talking with Tahu Nuva. Seeing that they have no chance against 12 Toa and Axonn, the Piraka decide to go into hiding, and plan to wait until the right moment to strike back. After a discussion, it is agreed that the Toa Inika will continue the quest for the Mask of Life while the Toa Nuva depart, as it would seem that the Toa Nuva are destined to awaken Mata Nui, but the Toa Inika must save his life first. Tahu Nuva promises that the Toa Nuva will be waiting for the Inika when they return, and once the Inika are out of hearing range, Axonn confronts him and Tahu admits to having lied. He mentions a cryptic mission that the Toa Nuva now have that the Inika cannot be a part of, and expresses his hopes that the new Toa will survive.

After a discussion as to the Voya Nui Matoran, Axonn volunteers to watch over them so that the Toa Nuva won't have to take them to Metru Nui and so the Toa Inika will be free to pursue the Ignika. Axonn then opens a tunnel in the Matoran village leading down to the undersea realm, and watches them depart after a warning about the dangers they may face...

Characters

 * Toa Inika
 * Toa Nuva
 * Voya Nui Resistance Team
 * Piraka
 * Piraka Fusion
 * Axonn
 * Brutaka
 * Vezon and Fenrakk
 * Botar
 * Kardas
 * Piraka Fusion
 * Irnakk
 * Umbra
 * Two Great Beings
 * Mana Ko