Krana

Each Bohrok contained a parasitic Krana which acted as its brain and gave it its power.

It is believed that the krana, besides controlling the bohrok, provided the intelligence to the swarms.



History
The Krana were telepathically guided by Cahdok and Gahdok, twin queens of the Bohrok swarms.

The Krana, while the Bohrok's strength, was also its weakness: even the strongest Bohrok, without its Krana, became little more than an empty shell. That shell could then be programmed or trained to repair the damage it inflicted. One of the main functions of the Bohrok Va scouts was to replace a Bohrok's missing Krana. If a Krana felt threatened, it could eject from its Bohrok host. This left the host powerless, but if the Krana attached onto another being's face, it took control of the other being's mind and assimilated it into the swarm.

The Toa Mata collected 48 Krana, and placed them into special slots in the middle of the Bohrok nest. This unlocked the hiding places of six sets of Exo-Toa armor and the lair of the two dreadful Bahrag twins. When the Bahrag were defeated, the Bohrok shut down and the Matoran collected all their Krana, threw the Krana into pits and sealed them away.

Recently, the Toa Nuva were sent on a mission to free the Bahrag, so they could release the Bohrok to return the island of Mata Nui to what is was "in the Before-Time" as Lewa said.

Krana types
The eight types of Krana each had their own name and rank in the swarm.


 * Krana Xa: Are Swarm Commander Krana that lead their Bohrok on their mission.


 * Krana Za: Are Squad Leader Krana that have the ability to communicate telepathically with other Krana of the swarm. A Krana Za controlled Lewa and Turaga Matau for a period of time.


 * Krana Vu: Are Surveyor Krana that can let a Bohrok fly short distances ahead of the swarm to confirm that the path is clear.


 * Krana Ca: Are Clearance Worker Krana with strong defense shielding; these Krana spearhead the swarm's mission.


 * Krana Yo: Are Mole Krana that use their Bohrok to tunnel through anything on the island.


 * Krana Ja: Are Scout Krana. with radar-like senses that detect distant obstacles in the path of the swarm.


 * Krana Su: Are Worker Krana with colossal energy and they inhabit the strongest of Bohrok. They are always around when brute force is needed.


 * Krana Bo: Are Sentinel Krana that can see in the dark. They serve as night-time lookouts and lead their Bohrok into the darkest places on Mata Nui.

Krana Colors
Each breed of Bohrok and Bohrok Va wear a different colored Krana. These are below:

Blue: Tahnok

Orange: Gahlok

Red: Lehvak

Green: Pahrak

Yellow-Green: Nuhvok

Light Blue: Kohrak

Yellow: Tahnok Va

Purple: Gahlok Va

Dark Grey: Lehvak Va

Light Yellow: Pahrak Va

Black: Nuhvok Va

White: Kohrak Va

Trivia

 * The Fohrok, unlike Bohrok, were not controlled Krana.
 * The Krana would work just as well as a Kanohi on a Matoran's face.

Zyglak
The Krana were first created by the Great Beings using the leftovers of the process they used to create the Matoran. However, sometimes, instead of becoming Krana, the leftovers became violent, reptilian creatures called Zyglak. Shunned by all others, the Zyglak lived in the darkest, dirtiest places where no one else went, all the while nursing a hateful resentment towards Matoran, Toa, and anything else that had to do with the Great Spirit Mata Nui.