The wildlife across Mata Nui, Metru Nui, and in fact everywhere thoughout the BIONICLE universe, is rich and diverse. Some rahi creatures are mild and easily tamed, such as the Hydruka, while others are fierce and wild. A few are intelligent.

At times, many rahi have been taken over by Makuta's infected kanohi masks and forced into rampages against Matoran and Toa.