Hlóðynorm

Hlóðynorm, also called Lodeworms or Elemental Worms in Undercommon are a species of invertebrate that Dwarven scholars of the University of Deephold claim to have studied but that the zoology department of the Academia Ars Magicka et Mundana considers hypothetical and has not found sufficient proof of.

According to the University of Deephold they are massive invertebrate that can stretch for miles and miles.
They supposedly consume rock and earth which they then excrete in a superheated and molten state.
Their seasonal migration from deeper layers of the earth to those closer to the surface of the Great Cavern of Aman-ya is theorized to be the cause of the seasons witnessed by those dwelling in the cavern.

Furthermore and even more ridiculously the dwarven scholars claim that lodeworms are, in fact, the larval state of a drakoid species whose adult specimens have never been seen in Aman-ya.