Inktober Monstrosities: T for Thoqqua

The thoqqua, or rockworm, is a worm-like creature from the elemental plane of earth and/or fire, and it is suspected to be the larva stage of some terrible elemental creature, though no-one knows exactly which. They are said to burrow into this realm of existence from the elemental planes, or the center of the earth itself, melting and devouring rock as it goes.

It originally appeared in the Fiend Folio for first edition AD&D, then in the Monstrous Compendium Planescape Appendix III for the second edition, and finally in the Monster Manual for third (and 3.5) edition.