Subterranean worms were great, blind, pale, white-tentacled creatures that lived in the deepest tunnels of Onu-Wahi. They were believed to eat raw protodermis. The appearance of one was enough to shut down an Onu-Matoran mine for good.
The massive subterranean worm had dead-white, flailing tentacles. One of its tentacles could strike a tunnel wall so hard that the entire place shook. Onua thought that these creatures were just Matoran legend until he encountered one himself. Those who mined protodermis occasionally spoke of great tentacled worms that lived in the very deepest tunnels of Onu-Wahi. Some claimed that they ate protodermis and were attracted by the piles of ore gathered by the workers. The appearance of such a creature was enough to shut down a mine for good. The creature was blind, which made it easier for Onua and Whenua to avoid being captured by it. Whenua claimed that this creature existed on Mata Nui longer than both he and Onua and was reluctant to harm it, as it was a link to the past. Even when Onua Nuva was using the power of his Pakari Nuva, the worm easily tossed him aside with its tentacle. It was big and strong. Like so many other creatures of the underground, it was bleached white. It lived in constant darkness, so it was blind and navigated by hearing. It could roar angrily. Since it made up for its lack of sight with super-sensitive hearing, it could be driven away by making a very loud noise.