A set of Lehvak Krana. Top row: Xa, Za, Vu, and Ca. Bottom row: Yo, Ja, Su, and Bo. A Krana Xa can be seen in the Lehvak's "forehead".
Each Bohrok contains a parasitic Krana which acts as its brain and gives it its power.
History
The Krana are telepathically guided by the Bahrag, twin queens of the Bohrok swarms.
The Krana, while the Bohrok's strength, is also its weakness: even the strongest Bohrok, without its Krana, becomes little more than an empty shell. That shell can then be programmed or trained to repair the damage it inflicted. One of the main functions of the Bohrok Va scouts is to replace a Bohrok's missing Krana. If a Krana feels threatened, it can eject from its Bohrok host, this leaves the host powerless, but if the Krana attaches onto another being's face, it takes control of the other being's mind and assimilates 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.
Krana types
The eight types of Krana each have 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 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.