Thrum worms grow to around 8-10 feet long and weigh up to 200 pounds when fully grown. They are segmented. They have dry, rubbery, orange-brown hides and smell of soil. Their heads are somewhat snake-like, but are not sinister or sly looking, instead being somewhat docile and natural looking. A Thrum Worm's mouth has two rows of very small teeth that it can tuck inside its mouth when shooting its sonic ray.
Thrum worms are unusual, slow-moving worms often used by specialized gnome cavalry. The gnomes take advantage of the worms' burrowing abilities in several ways. In times of peace, they use their unique mounts to find ore and mineral deposits, and in times of war, they burrow behind enemy lines and infiltrate enemy encampments.
A thrum worm can be trained with the use of the Handle Animal skill. Riding a thrum worm requires an exotic saddle or a specialized burrower's saddle. They are somewhat easier to tame and ride than other magical beasts.
Thrum worms generally avoid combat when they can. When forced to fight by a burrowing predator or when directed to fight by a rider or handler, the thrum worm relies on its sonic ray as its primary attack form.
The sonic ray can be fired from a Thrum Worm's mouth once per day, with a range of 30 feet and no range increment.