Bohrok

The Bohrok were a race of hive-minded, mechanical insectoid creatures, controlled by strange, parasitic creatures within their heads known as Krana.

Types
The following Bohrok had similar elements to the Toa Mata/Nuva:
 * Tahnok: Fire
 * Gahlok: Water
 * Lehvak: Acid
 * Pahrak: Stone
 * Kohrak: Ice
 * Nuhvok: Earth

Creation
The creators of the first Bohrok were the Great Beings. The Great Beings also created the Bohrok-Va and Bahrag and placed them in a series of tunnel networks under Mata Nui. More Bohrok are created when an Av-Matoran life-span ends.

Brotherhood of Makuta
In the service of the Brotherhood of Makuta, Teridax's Toa Hagah team once encountered and defeated a Bohrok swarm. A theory is that the reason why Teridax awakened the Bohrok was to buy himself time to become stronger. It is likely that the Brotherhood began experiments and studies on the Bohrok, the results being the Fohrok, or "fake Bohrok". These Fohrok would fight in their forces for many years, their chassis a stark blue and yellow.

Metru Nui
In Metru Nui, Onu-Matoran miners stumbled upon a Bohrok nest and found that the creatures were fully mechanical while the Krana they carried inside were completely organic. After a quick check, archivists found there was no evidence of assembly. Another Onu-Matoran archivist named Mavrah theorized that the Bohrok were once biomechanical, but evolved to a state with no organic parts and without a single independent thought. Although the Archives were eventually destroyed, the Bohrok nest was untouched. However, word of their sleeping threat somehow spread to the public, including the Toa Metru.

Early Signs
Bohrok were since subtly warned against by the Toa Metru-turned-Turaga and, on Mata Nui, signs began to appear in various places. Inscribed on a rock in Le-Wahi were the ominous words, "Wake one, and you wake them all " (seen left). There was yet another sign near Ko-Koro, carved graffitically into a statue of Mata Nui. It said "Beware the swarms". During his time in Ko-Wahi, Takua received a vision of the Bohrok symbol.

Awakening
Takua would later play a major role in the awakening of the Bohrok. At the climax of the battle against Teridax in Mangaia, he would record- and create -history. When the Toa Mata defeated Teridax, the evil spirit subtly went to the part of chambers that connected to the Mata Nui Bohrok Nest. He opened the gate and used his sound powers to mimic the usual wake up call for the swarms. The curiosity of Takua got the better of him, and he wandered inside. The words, "Wake one, and you wake them all" came to fruition. Takua barely escaped using an ancient chute, but the Bohrok were still awakened.

The Bohrok War
During the beginning of the cleansing, the Bohrok showed no interest whatsoever in the Matoran, simply seeking to fulfill their mission and attacking only when directly threatened. However, after encountering resistance from them and the Toa, they began to target the villages to subdue the resistance, using the various tactics of the swarms. Based on the fact that they have styles of combat, it seems that they were programmed to be able to, should some beings take residence on the island.

Surprise Strike
Expecting a great victory celebration for the defeat of Makuta, the Toa returned to their respective Koro only to find with horror that new, insect-like robots were starting to destroy them. In Ta-Koro, the deterioration was especially great and it was the site of the first battle and victory for the Matoran. The Bohrok easily felled large trees, froze lava, melted ice and leveled mountains in their devastating quest to "clean it all".

Skirmishes and Counter-Attacks
The Toa fought in several difficult battles involving all of the elements, but it was at the home front where the real battle was fought. Lewa shockingly found that the whole of Le-Koro had been taken over by Krana and put into the hive. Taking the Matoran hostage, Bohrok-Matau forced Lewa to wear one himself and subject to their will. Only Tamaru and Kongu escaped the massive brainwashing. Meanwhile, Kopaka discovered the second entrance to the Bohrok nest at Mount Ihu.

Boxor
At Onu-Koro, the village and mines were being flooded by a Gahlok squadron. Needing to improvise, the inventor, Nuparu found for the first time in 1000 years that the Bohrok were mechanical. This vital fact allowed the Onu-Matoran to reverse-engineer a defeated member of the Bohrok squadron of Ga into fearsome new fighting machines that would turn the tide: Boxor. Boxor were specifically designed to battle Krana-controlled beings by using quick jabs and punches to knock them off their feet. They were extremely effective and liberated the Koro from several attacks, including - with the help of an ambush planned by Takua, Kongu and Tamaru - Le-Koro's Krana infestation. However, they weren't foolproof.

Endgame
Ga-Koro was attacked by a Pahrak swarm in an infamous battle where the Boxor were for the first time defeated and a new kind of Kolhii was invented.

The Toa were finally free to take the battle to the Bohrok and they went inside a strangely empty nest. They found buried Exo-Toa, placed there in the case that the Bohrok rose up. The Toa used them to fight the Bahrag, but soon found that it limited their elemental powers that allowed them to defeat Makuta and his minions in the first place. They shed the armor and used their elemental energy to defeat the Bahrag by imprisoning them in a protodermis cage, but not before transforming in chutes of energized protodermis, forever becoming the Toa Nuva.

Legacy
The Bohrok lost their Krana and were reprogrammed to serve the Matoran. However, this lasted only briefly, as they were destroyed or put back to sleep by the Bohrok-Kal.

Later on, the Toa Nuva came back to reawaken the Bohrok so they could clean the island of Mata Nui as part of their "to-do list" (which had been given to them by Axonn) that needed to be completed in order for Mata Nui to be revived. The Bohrok were used to help Mata Nui by loosening the ground to allow him to rise. They completed their mission and went finally back to sleep to await their next summoning.

Later, during the siege of Metru Nui between the Order of Mata Nui and the Brotherhood of Makuta, Krakua awoke the nearby Bohrok Swarms on the incoming Brotherhood soldiers.

Swarms and Systems
The Bohrok swarms are divided into six clans: Tahnok, Gahlok, Lehvak, Pahrak, Nuhvok, and Kohrak. Each has a unique style of war, thought, and "cleansing".

Bohrok Va
The Bohrok Va were secondary Bohrok, or "drones". They did the duties of Krana-exchange, courier, strategist, and general petty work. While not as powerful as their brethren, they could be considered smarter, and can still put up a fight. They often carried new krana to Bohrok who have lost theirs. The source of these krana was the Bahrag.

Powers
Bohrok have the ability to curl up into a ball and eject their Krana onto an opponent, making them a "host". Each Bohrok is also equipped with "hand" shields that allow them to fire their specific "cleaning" agent, be it acid, flame, or otherwise.

Kaita - Bohrok also have the ability to unite and form Kaita. However, they were never seen doing this.

Krana
Krana were intrinsic to the Bohrok swarms; without them they were blank slates that could be put to good use by other beings via reprogramming. The Krana formed a telepathic bond with the Bohrok and each other, effectively forming a network ultimately controlled by the Bahrag. The Krana also gave them additional powers that were crucial in the Bohrok's success of their mission.

Bahrag
The Bahrag were the Bohrok's two illustrious queens, Cahdok and Gahdok, leading a biumvirate. They held all the powers of the six swarms, and controlled and created the Krana, dipping them into some kind of protodermis. They also had the ability to project illusions and grow stronger in proximity to each other, which was useful against the Toa. In the case of their being compromised, the Bohrok-Kal, who had Krana-Kal, would take over. At the end of their mission their Krana-Kal would turn a silver color and grant the Bohrok-Kal a special form of shielding that made them immune to anything that would surpress, foil or slow them down in their last few moments until the completion of their mission.

Evolution
An Onu-Matoran, Mavrah, once theorized that Bohrok were not built, but were bionic creatures that had somehow evolved to the point where all organic matter was lost and substituted for mechanics. It would have meant going from possibly a living, intelligent being to a form of artificial life incapable of independent thought. This was proved when the Toa Nuva figured out that a percentage of Av-Matoran were destined to transform at some point in their lives into Bohrok then be fitted with Krana.

Creation by the Great Beings
Some held the belief that the Bohrok were created and later changed by the Great Beings, like everything else. However, the Bohrok are actually Av-Matoran who are destined to become Bohrok. This was proven by the Toa Nuva during their visit to Karda Nui when Tahu witnessed a Av-Matoran who just helped him transform into a Bohrok, and being immediately teleported to the Mata Nui Bohrok Nest.

Trivia

 * It was hinted that the Toa Mata and the Bohrok were somehow related, based on a comment by the Bahrag.: "You dared oppose your brothers!" This refers to the fact that both the Toa Mata/Toa Nuva and Bohrok serve Mata Nui, as well as the fact that they come from the same source, as most Toa came into being as Matoran and Bohrok are the final stage in the lifecycle of Av-Matoran.
 * The only Bionicle film that the Bohrok appeared is Mask of Light where they are found frozen in Ko-Koro, even scaring Jaller and Takua.
 * Some Bohrok appeared in the Maze of Shadows video game. They were not controlled by Krana, but rather by worm-like creatures that had escaped a Brotherhood of Makuta lair. They found their way into a Bohrok nest, took over some Bohrok shells and learned how to use them to defend themselves.
 * The Great Beings designed the Bohrok after Baterra.

Appearances

 * Mata Nui Online Game
 * Chronicles 2: Beware the Bohrok
 * Chronicles 3: Makuta's Revenge
 * Mask of Light (cameo)
 * Legends 7: Prisoners of the Pit
 * Legends 10: Swamp of Secrets
 * Heroes (non-canon)