Bohrok (Earth-4001)

The Bohrok are a race of hive-minded, mechanical insectoid creatures. They are controlled by strange creatures known as Krana.

History
The history of the Bohrok is the same as their mainstream counterparts.

Swarms & 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, delivery, strategizing, and general petty work. While not as powerful as their brethren, they could be considered smarter, and could still put up a fight. They often carried new Krana to Bohrok who have lost theirs. The Bahrag provided them with these replacement Krana.

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.

Bohrok also have the ability to form more powerful Bohrok Kaita. However, they were never seen doing this.

Krana
Krana were intrinsic to the Bohrok swarms; without them, they were blank slates. The Krana formed a telepathic bond with the Bohrok and between each other, effectively forming a network ultimately controlled by the Bahrag. These Krana also gave them additional powers.

Bahrag
The Bahrag were the Bohrok's two illustrious queens named Cahdok and Gahdok. They held the powers of all six Bohrok swarms and controlled the Krana, which they would create by dipping an unknown substance into what appeared to be protodermis. They also had the ability to project illusions, and grow stronger in close proximity to each other, which proved useful against the Toa. In case the Bahrag were ever compromised, the Bohrok-Kal would take over. The Bohrok-Kal were controlled by Krana-Kal, which were more powerful versions of Krana. The Bohrok-Kal's mission was to free the Bahrag, should they ever be imprisoned. When they came close to achieving their goal, their Krana-Kal would turn a silver color, and project a shield to protect the Bohrok-Kal from harm as they finished the task.

Evolution
An Onu-Matoran named Mavrah once theorized that the Bohrok were not built, but were bionic creatures that had somehow evolved to the point where all organic matter was lost. 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 some point in their life 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, scaring Jaller and Takua.
 * Some Bohrok appeared in the Maze of Shadows video game. These Bohrok 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 Forerunners designed the Bohrok after the Baterra.