Tunneler

Tunnelers were large lizard-like Rahi that ate any inorganic protodermis they came across. They also had the ability to absorb any power used on them, for example, becoming a creature of fire when exposed to fire. This can also be a weakness as evident in Bionicle Adventures #2. Where if it is exposed by something like glass it can be stopped.

Toa Metru Vakama and Onewa encountered a very large Tunneler during their search for Po-Metru's Great Disk. They defeated it by turning it into glass.