Reference
Rahi
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