Kyunei was one of many Matoran kidnapped by the Brotherhood of Makuta for their Nui-Matoran project. After being put through a number of experiments, Kyueni emerged as one of roughly twenty surviving Matoran who were brainwashed and sent to be cared for and trained by various Makuta. In the wake of a Nui-Matoran killing his guardian, a message was sent for all the Nui-Matoran to be put to death. When she was attacked, Kyueni's mental restraints were broken, and she managed to use his powers to escape.
After stowing away on a ship, Kyueni jumped ship at the first port it came, too. She found she had been subconsciously drawn there, due to the presense of Taluu, another Nui-Matoran. The pair soon became friends and settled into the village. Several years later, the Brotherhood caught up with them, and when they ran, proceeded to destroy the village that had harbored them. Horrified by this, Kyueni made it her personal mission to find any other surviving Nui-Matoran and gather them together, to protect themselves and those that would otherwise harbor them. Using her powers, she managed to locate Nixan and tried to convince him to join her and Taluu. After failing at that, the pair left Nixan's village, Umai, and were attacked by the Skakdi Kreba shortly thereafter. Kyueni sent out a psychic cry for help to Nixan and his roommate Krenshar for help. When both came, the four were able to defeat Kreba. After assessing the situation, they agreed to allow Kreba to accompany them, and the five of them set out for Aleris where Kyueni could sense other Nui-Matoran.
Kyueni was granted all manner of psychic abilities by the Brotherhood through the Nui-Matoran project, ranging from telepathy to mind control. She has also shown herself capable of feeding another being thoughts and memories. Her powers are also fueled by her emotions, the more intensely she feels, the more power she gains.
Kyueni may seem very calm and placid, like many of her tribe, but her powers have caused her to have to surpress her emotions. If left unchecked, her emotion-fueled powers can spiral out of control. Despite this, she is very wise and intuitive; she is very good at reading other people, even without the aid of her powers. She considers Taluu her best friend, but is prone to obsess over her self-appointed mission and neglect their friendship.