Bohrok

The Bohrok are mechanical insectoid creatures, controlled by strange, parasitic creatures within their heads, known as Krana. If a Bohrok loses its Krana, it shuts down and can be reprogrammed to do one's bidding, but if a Krana gets on another being's face, it then assimilates its host into the swarm. The Krana, which control the Bohrok, are in turn controlled by the two fearsome Bahrag, twin queens of the swarms. The Bohrok Va, not controlled by Bahrag, replaced the lost Krana.

History and Overview
Over a thousand years ago 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 (like every other Bionicle lifeform), but evolved to a state with no organic parts and without a single independent thought.

The Bohrok swarms are shrouded in mystery: no one knows how, where or when they were made. What is known is that these insect-like creatures were made for one purpose: to restore the island of Mata Nui to the "Before-Time," when its surface was completely barren. The Bohrok were not supposed to smash the island to bits while it was still inhabited by Matoran; however, the evil Makuta awoke the sleeping swarms early, causing them to commence their task of destruction. The Bohrok easily felled large trees, froze lava, melted ice, and leveled mountains in their devastating quest to "clean it all". Relief came only when the Toa Mata defeated the Bohrok Queens, the Bahrag, in a dramatic quest. Without the Bahrag to guide them, the Bohrok became docile, and the Matoran put them to work repairing the damage.

Shortly afterward, six mutated Bohrok called Bohrok-Kal were released. These elite Bohrok were much more powerful and intelligent - and independent - than regular Bohrok. Their mission was to release the Bahrag from where they had been imprisoned by the Toa Mata, thus enabling the Bohrok swarms to resume their invasion, but failed and defeated by the Toa Nuva.

Currently, the Bohrok have returned to their nests (by the Bohrok-Kal command). Now that the Matoran have left the island, the Bohrok are now free to do their cleaning - or would be, if the Bahrag weren't still imprisoned.

Some Bohrok appeared in the Maze of Shadows video game, which took place well before the swarms were awakened. It turns out that these Bohrok were not controlled by Krana, but rather by hive-minded worm 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.

Powers
All Bohrok share the abilities of curling up into a ball and ejecting their Krana onto an opponent. Each Bohrok is also equipped with "hand" shields with that allow them to fire their element. In addition, the Bohrok's Krana gives it an additional power, and a Bohrok can switch these powers by having a Bohrok Va exchange its Krana for another.