Beware the Rahi!
The Rahi are evil beasts who aid Makuta! Powerful and dangerous, they’re out to stop the Toa from collecting the Masks of Power. Each Rahi has a special attack function designed to rob the Toa of their masks. Only by removing the Rahi’s infected masks can the Toa hope to tame them.
Source: BIONICLE #2: Deep Into Darkness
Powerful beasts who serve Makuta
Source: The Official Guide to BIONICLE