We now return to the subterranean ecosystems in order to meet a truly interesting species.

The Gribble is a distant relative of the Orester and arguably the most intelligent underground species. This creature is a cavern gardener; much like its larger, more lumbering relative, it carries a variety of fungi and moss on its rocky shell. Once a Gribble discovers a baren cavern, it will gently break off patches of moss and fungi in order to aid them in spreading and creating a more temperate environment.
Just like Oresters, Gribbles are geovores, meaning that they feed on minerals in order to gain sustenance. The mana crystals and mana cores that are a part of their body are prominent enough to make these critters significantly more active; larger crystals mean more magical energy to process ingested matter which in turn provides more energy to function.

As mentioned above, Gribbles are intelligent creatures. In fact, they are even sapient and can interact with humanoids in a friendly manner. A diet of rocks makes it so that they don't have any predatory instinct, and surface dwellers are different from their natural predators to such an extent that they don't perceive them as a threat.
Communication is possible via pantomime or telepathy-based spells. Scholars are however looking for alternative means of communication...other than verbal, since Gribbles are physically incapable of replicating sounds that humanoids produce and vice-versa; the sounds they produce are best described as "gravely" (like gravel rubbing against gravel at different pitches and intervals).