Turahk was the major antagonist that appeared in the BIONICLE series and the secondary antagonist of the 2003 storyline. He was also the leader of the six Rahkshi released by Makuta Teridax in an attempt to prevent the approach of the seventh Toa. Turahk is known as the Rahkshi of Fear and he have the ability to spread fear and panic towards his opponents through the power from his Staff of Fear.
Among of all the Rahkshi, Turahk was extremely loyal to Teridax as he was willing to complete the misssion of hunting down Takua to prevent him from fighting the 7th Toa.
Following the defeat of the three Rahkshi: Guurahk, Lerahk and Panrahk at the hands of Kopaka in Ko-Koro in the island of Mata Nui, Teridax decided to use the Kraata to create three new Rahkshi; Turahk, Kurahk and Vorahk. He believed that their powers would eventually destroy the Toa's destiny. After creating them, he sent them to find the two Matoran Jaller and Takua and prevent them from searching for the Toa of Light.
Turahk, Kurahk and Vorahk invaded Onu-Koro and start attacking the Matoran. As they advanced toward Takua, Pohatu and Onua tried to take them down and were defeated. Vorahk drained Onua's power, and Pohatu was hit by Turahk's fear energy. When the rest of the Toa Nuva arrived, Tahu was hit by Kurahk's anger power, causing him to turn on his friends. In the ensuing chaos, Turahk went after Takua. But Tahu was frozen in ice by Kopaka, and Onua brought down the cave's ceiling on the Rahkshi, seemingly killing them.
However, Turahk and the other two Rahkshi survived the collision. They joined Guurahk, Lerahk, and Panrahk as they tracked Takua and Jaller to Kini-Nui. They cornered the Matoran just as the Toa Nuva arrived to save them. In the ensuing battle, the Toa Nuva were able to work together as a team and overpower the Rahkshi.
After the other five Rahkshi were defeated, Turahk began chasing after Jaller and Takua before being intercepted by Pewku, an Ussal Crab. But he threw her aside and use his Staff of Fear to trap Takua in a wall of terror. Turahk then used his staff to finish off Takua, only to be intercepted by Jaller, who sacrificed himself by getting himself killed by the energy blast. Turahk was then attacked by Gali and Pohatu, but he defeated them both. He then prepare dto kill Takua but Takua donned the Kanohi Avohkii and transform into Takunuva, the Toa of Light. Turahk then tried to attack Takanuva but was eventually overwhelmed by the latter's power and was incinerated by him with his beam of light, causing his armor and the Kraata to melt into nothingness.
Turahk's body was later used to build the Ussanui, along with the other Rahkshi.
BIONICLE: HeroesHere, Turahk serves as one of the bosses alongside the Titans and his brethren in the game. He was encountered in the Scorched Earth level of Hakann's volcano. Like his appearance in the series, Turahk wields the power of Fear and also carried the Staff of Fear, that resembles his set form rather than the animation version of the staff.
- Teridax chose to sent Turahk to stop the arrival of Takanuva because Fear was in direct opposition to the Ta-Matoran Principle of Courage based on his color scheme.