In the LEGO BIONICLE universe, each Bohrok contains a parasitic Krana which acts as its brain and gives the Bohrok its power. Enhanced Bohrok called Bohrok-Kal have similarly enhanced Krana called Krana-Kal.
The Krana are intelligent organisms that are telepathically guided by the Bahrag, twin queens of the Bohrok swarms. With this guidance, they control and direct the inanimate Bohrok shells to do the Bahrag's bidding.
Krana were originally created by the Great Beings, by exposing the leftovers from the process of creating Matoran to energized protodermis. However, some of this material became not Krana, but a reptilian race called the Zyglak (see "Zyglak", below) In the present time, the Bahrag immerse some unknown matter into energized protodermis instead of Matoran leftovers, without the risk of creating Zyglak.
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 (eight types of Krana times six types of Bohrok), 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-Kal are specialized Krana, mutated to have stronger abilities. Like regular Krana are literally the brains of the Bohrok, the Krana-Kal are the driving force of the Bohrok-Kal. The Krana-Kal are unlike the other Krana in the way that they can act independently, without depending on the Bahrag; and they are able to communicate with other beings via telepathy. Krana-Kal also contain a unique property which allows them to turn a silver and gold color and generate an impenetrable shield around their hosts when at the final stages of their mission.
The eight types of Krana each have their own name and rank in the swarm. Krana-Kal, though having identical shapes and similar names to ordinary Krana, have slightly different ranks and powers.
- Krana Xa are Swarm Commander Krana that lead their Bohrok on their mission.
- Xa-Kal are Liberator Krana; the most important of the Krana-Kal, one of these must be brought into physical contact with the Bahrag to complete the Bohrok-Kal's 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.
- Za-Kal are Overseer Krana that can communicate telepathically with other Krana-Kal and have the limited ability to read minds and sense strong emotions.
- Krana Vu are Surveyor Krana that can let a Bohrok fly short distances ahead of the swarm to confirm that the path is clear.
- Vu-Kal are Transporter Krana that can move its Bohrok-Kal host over the surface or through the air at great speed.
- Krana Ca are Clearance Worker Krana with strong defense shielding; these Krana spearhead the swarm's mission.
- Ca-Kal are Seeker Krana that are linked to the Bahrag and can sense their presence within a limited range.
- Krana Yo are Mole Krana that use their Bohrok to tunnel through anything on the island.
- Yo-Kal are Excavator Krana that can sense stress points in the earth and detect underground movement.
- Krana Ja are Scout Krana. with radar-like senses that detect distant obstacles in the path of the swarm.
- Ja-Kal are Tracker Krana that can detect distant obstacles and enhance all of the senses of the Bohrok-Kal.
- Krana Su are Worker Krana with colossal energy and they inhabit the strongest of Bohrok; they are always around when brute force is needed.
- Su-Kal are Demolisher Krana that provide tremendous strength, endurance and resistance to heat and cold.
- 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.
- Bo-Kal are Visionary Krana that can see in the dark and through any substance except for the floors and walls of the Mata Nui underground.
Each Bohrok breed uses Krana of different colours. There are actually two colours per breed: a Krana is its "active" colour when controlling a Bohrok or some other being, and changes to its "inactive" colour at all other times. This inactive colour is sometimes thought of as a Bohrok Va Krana, as their job is to carry around spare, inactive Krana. In addition, Krana-Kal have their own metallic colours.
Each Bohrok, Bohrok Va, and Bohrok-Kal set came with one random Krana of the appropriate colour. Further Krana could be collected from Krana packs produced by LEGO, so that all 144 variations could be found. Rare silver Krana Xa-Kal were also made; 5,000 of white metal and 72 of actual sterling silver; included at random in North American and United Kingdom Bohrok-Kal sets. If you have the Toa Mata or Toa Nuva toys, the Krana masks can be attached to the unmasked faces.
An accident of the Krana's original creation by the Great Beings, the Zyglak are a savage reptilian race. Shunned by their creators and universally despised, the Zyglak retreated to dark, desolate areas, all the while harboring bitter hatred against the Matoran, their Great Spirit, and all loyal to them.
Zyglak are amphibious, and live in desolate areas where nobody else will go. The Toa Inika encountered some in the stone cord that connects Voya Nui and Mahri Nui, and some of the Barraki found a group in the ruins of the original Pit. Toa Lesovikk also discovered that Karzahni rounded up Zyglak to help him attack Mahri Nui.
Zyglak carry knives, spears, and other weapons with blades that destroy whatever they hit. It is unknown if or how they are affected by the Pit's mutagenic waters (the mutagen is thin in the deepest part of the Pit were the Zyglak live). They are also known to carry a dangerous organic-protodermis destroying disease which is spread to other beings through touch.
Sets that include Krana / Krana-Kal
- 8559 Krana
- 8569 Krana
- 8597 Krana Nuva
- 8598 Krana Nuva
- 8599 Krana-Kal
- 8600 Krana-Kal
- 8563 Tahnok
- 8562 Gahlok
- 8564 Lehvak
- 8560 Pahrak
- 8561 Nuhvok
- 8565 Kohrak
- 8554 Tahnok Va
- 8550 Gahlok Va
- 8552 Lehvak Va
- 8553 Pahrak Va
- 8555 Nuhvok Va
- 8551 Kohrak Va
- 8574 Tahnok-Kal
- 8578 Gahlok-Kal
- 8576 Lehvak-Kal
- 8577 Pahrak-Kal
- 8573 Nuhvok-Kal
- 8575 Kohrak-Kal
General information comes from the BIONICLE Chronicles book series.