Krahka was the name of an individual Rahi.
The History of Krahka and her species remains largely vague. As they were an intelligent species of Rahi, it is likely that they were created by the Brotherhood of Makuta. It is also known that Krahka's species was then placed on an unnamed island, where they took residence and likely evolved to a more intelligent state of being. However, Krahka later stated that she was the last of her kind, indicating the others had been killed off at some point.
Due to unknown reasons, Krahka was transported to Metru-Nui. Upon arriving, she felt threatened by the large population of Matoran and took shelter in the sub-levels of the Archives; an area where only the most dangerous Rahi were kept away from the Matoran.
Following an Onu-Matoran named Nuparu wondering around the Sub-Levels; in search of Rahkshi armor to use for experiments, he stumbled across a leak in the structure. Fearing the worst he reported his finding to the Toa Metru as they headed to the Coliseum after defeating the Morbuzakh. Understanding the threat that the leak meant to the Archives Structure, Toa Whenua decided to help. This forced the other Toa to help as well and the Team then entered the Archives. Krahka followed them from their first entry and, as they split up, took the form of a Rahkshi of Insect Control. She managed to overwhelm Nokama by using a swarm of Fireflyers then shape-shifted into the Toa of Water's form, giving her access to the Toa's Elemental Powers but not to her vocabulary.
Still in the form of Nokama, Krahka was confronted by Vakama as their two separate tunnels converged. Still unable to speak Matoran, Krahka was forced to repeat broken fragments of words that Krahka had said. This tipped Vakama off that something was wrong with Nokama, but Krahka managed to overwhelm him too with Nokama's Water Powers, knocking him unconscious.
Following her encounter with the Toa of Fire, she changed her form to imitate him and continued. She eventually came across Onewa while in Vakama's form and used her newly-acquired Fire Abilities to render Onewa unconscious. After assuming his form too, Krahka's tunnel then converged on Matau's. She trapped the Toa of Air under a wall of stone, not bothering to knock him out or assume his form. She then left to pick off Whenua as she sensed his knowledge of her territory and saw him as her biggest threat. In order to evade suspicions, she took his form and returned the other Toa. By the time she had returned, Matau and Nuju, Vakama, Nokama, and Onewa had formed factions against each other, believing they had each been attacked by another member of the group. Krahka, in the form of Whenua, informed them of 'Krahka' and referred to herself as an intelligent Rahi. She then led the other Toa deeper into the Archives in the form of the Toa of Earth.
While in the Toa's form,